diff --git a/compact/definitions.xml b/compact/definitions.xml
index c4ec7b2d09..f937e1d5b4 100644
--- a/compact/definitions.xml
+++ b/compact/definitions.xml
@@ -9,10 +9,17 @@
     <documentation>
       ## World volume
     </documentation>
-    <constant name="world_side" value="30*m"/>
-    <constant name="world_dx" value="world_side"/>
-    <constant name="world_dy" value="world_side"/>
-    <constant name="world_dz" value="100*m"/>
+    <constant name="backward_x0" value="0.5*m"/>
+    <constant name="backward_dx" value="2*m"/>
+    <constant name="backward_dy" value="1*m"/>
+    <constant name="backward_dz" value="40*m"/>
+    <constant name="exp_hall_dx" value="3.5*m"/>
+    <constant name="exp_hall_dy" value="3.5*m"/>
+    <constant name="exp_hall_dz" value="5.5*m"/>
+    <constant name="forward_x0" value="-1*m"/>
+    <constant name="forward_dx" value="2*m"/>
+    <constant name="forward_dy" value="1.5*m"/>
+    <constant name="forward_dz" value="25*m"/>
 
     <documentation>
       ## Detector IDs
diff --git a/compact/far_forward/vacuum.xml b/compact/far_forward/vacuum.xml
index 15b2688ca6..cb3dd62d41 100644
--- a/compact/far_forward/vacuum.xml
+++ b/compact/far_forward/vacuum.xml
@@ -59,6 +59,8 @@
                 <aperture x="B2PF_InnerRadius*2" y="B2PF_InnerRadius*2"  r="B2PF_InnerRadius" />
         </element>
 
+        <end_of_the_world z="exp_hall_dz + 2.0 * forward_dz"/>
+
       </detector>
   </detectors>
 
diff --git a/compact/tracking/central_tracker_hybrid_v2.xml b/compact/tracking/central_tracker_hybrid_v2.xml
index 925192edfe..a4aa68a661 100644
--- a/compact/tracking/central_tracker_hybrid_v2.xml
+++ b/compact/tracking/central_tracker_hybrid_v2.xml
@@ -156,8 +156,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="InnerTrackerBarrelSupportCone_rmax1" value="InnerTrackerBarrelSupportCone_rmin1 + SiTrackerSupportConeCF_thickness" />
     <constant name="InnerTrackerBarrelSupportCone_rmin2" value="InnerTrackerBarrelServiceCone_rmax2" />
     <constant name="InnerTrackerBarrelSupportCone_rmax2" value="InnerTrackerBarrelSupportCone_rmin2 + SiTrackerSupportConeCF_thickness" />
-    <constant name="InnerTrackerBarrelLayer1_length"     value="InnerTrackerBarrelMod1_length + 1*um" />
-    <constant name="InnerTrackerBarrelLayer2_length"     value="InnerTrackerBarrelMod2_length + 1*um" />
+    <constant name="InnerTrackerBarrelLayer1_length"     value="InnerTrackerBarrelMod1_length" />
+    <constant name="InnerTrackerBarrelLayer2_length"     value="InnerTrackerBarrelMod2_length" />
     <constant name="InnerTrackerBarrelLayer_thickness"   value="1.1*cm" />
     <comment> Place asymmetrically in the layer (module sits near the bottom). </comment>
     <constant name="InnerTrackerBarrelLayer1_rmin"       value="InnerTrackerBarrelMod1_rmin - InnerTrackerBarrelLayer_thickness / 25" />
@@ -238,7 +238,7 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <comment> Global Si endcap variables </comment>
     <constant name="SiTrackerEndcapMod_thickness"   value="SiTrackerEndcapCF_thickness + SiTrackerEndcapAl_thickness + SiTrackerSensor_thickness" />
     <constant name="SiTrackerEndcapMod_angle"       value="360.0*degree / SiTrackerEndcapMod_count * (1 + SiTrackerEndcapMod_overlap)" />
-    <constant name="SiTrackerEndcapLayer_thickness" value="SiTrackerEndcapMod_thickness + 2 * SiTrackerEndcapMod_dz + 1*um" />
+    <constant name="SiTrackerEndcapLayer_thickness" value="SiTrackerEndcapMod_thickness + 2 * SiTrackerEndcapMod_dz" />
     <constant name="SiTrackerServiceCyl_rmin" value="SiTrackerCyl_rmin"/>
     <constant name="SiTrackerServiceCyl_rmax" value="SiTrackerServiceCyl_rmin + SiTrackerServiceCylAl_thickness"/>
     <constant name="SiTrackerSupportCyl_rmin" value="SiTrackerServiceCyl_rmax"/>
@@ -259,11 +259,11 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="InnerTrackerEndcapMod2_x2"    value="2 * InnerTrackerEndcapMod2_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="InnerTrackerEndcapMod2_y"     value="InnerTrackerEndcapMod2_rmax * cos(SiTrackerEndcapMod_angle/2) - InnerTrackerEndcapMod2_rmin" />
 
-    <constant name="InnerTrackerEndcapLayer1_rmin"        value="InnerTrackerEndcapMod1_rmin - 1*um" />
-    <constant name="InnerTrackerEndcapLayer1_rmax"        value="InnerTrackerEndcapMod1_rmax + 1*um" />
+    <constant name="InnerTrackerEndcapLayer1_rmin"        value="InnerTrackerEndcapMod1_rmin" />
+    <constant name="InnerTrackerEndcapLayer1_rmax"        value="InnerTrackerEndcapMod1_rmax" />
     <constant name="InnerTrackerEndcapLayer1_zmin"        value="InnerTrackerEndcapMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
-    <constant name="InnerTrackerEndcapLayer2_rmin"        value="InnerTrackerEndcapMod2_rmin - 1*um" />
-    <constant name="InnerTrackerEndcapLayer2_rmax"        value="InnerTrackerEndcapMod2_rmax + 1*um" />
+    <constant name="InnerTrackerEndcapLayer2_rmin"        value="InnerTrackerEndcapMod2_rmin" />
+    <constant name="InnerTrackerEndcapLayer2_rmax"        value="InnerTrackerEndcapMod2_rmax" />
     <constant name="InnerTrackerEndcapLayer2_zmin"        value="InnerTrackerEndcapMod2_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <constant name="InnerTrackerEndcapCone_zmin"          value="InnerTrackerBarrelCone_zmax" />
@@ -565,8 +565,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="MedialTrackerEndcapPMod1_x2"    value="2 * MedialTrackerEndcapPMod1_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="MedialTrackerEndcapPMod1_y"     value="MedialTrackerEndcapPMod1_rmax * cos(SiTrackerEndcapMod_angle/2) - MedialTrackerEndcapPMod1_rmin" />
 
-    <constant name="MedialTrackerEndcapPLayer1_rmin"  value="MedialTrackerEndcapPMod1_rmin - 1*um" />
-    <constant name="MedialTrackerEndcapPLayer1_rmax"  value="MedialTrackerEndcapPMod1_rmax + 1*um" />
+    <constant name="MedialTrackerEndcapPLayer1_rmin"  value="MedialTrackerEndcapPMod1_rmin" />
+    <constant name="MedialTrackerEndcapPLayer1_rmax"  value="MedialTrackerEndcapPMod1_rmax" />
     <constant name="MedialTrackerEndcapPLayer1_zmin"  value="MedialTrackerEndcapPMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <constant name="MedialTrackerEndcapNMod1_zmin"  value="MedialTrackerEndcap_zmin" />
@@ -576,8 +576,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="MedialTrackerEndcapNMod1_x2"    value="2 * MedialTrackerEndcapNMod1_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="MedialTrackerEndcapNMod1_y"     value="MedialTrackerEndcapNMod1_rmax * cos(SiTrackerEndcapMod_angle/2) - MedialTrackerEndcapNMod1_rmin" />
 
-    <constant name="MedialTrackerEndcapNLayer1_rmin"  value="MedialTrackerEndcapNMod1_rmin - 1*um" />
-    <constant name="MedialTrackerEndcapNLayer1_rmax"  value="MedialTrackerEndcapNMod1_rmax + 1*um" />
+    <constant name="MedialTrackerEndcapNLayer1_rmin"  value="MedialTrackerEndcapNMod1_rmin" />
+    <constant name="MedialTrackerEndcapNLayer1_rmax"  value="MedialTrackerEndcapNMod1_rmax" />
     <constant name="MedialTrackerEndcapNLayer1_zmin"  value="MedialTrackerEndcapNMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <comment> The tracker endcap ends at the same place as the outer tracker barrel that sits around it </comment>
@@ -762,8 +762,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="OuterTrackerEndcapPMod1_x1"    value="2 * OuterTrackerEndcapPMod1_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapPMod1_x2"    value="2 * OuterTrackerEndcapPMod1_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapPMod1_y"     value="OuterTrackerEndcapPMod1_rmax * cos(SiTrackerEndcapMod_angle/2) - OuterTrackerEndcapPMod1_rmin" />
-    <constant name="OuterTrackerEndcapPLayer1_rmin"  value="OuterTrackerEndcapPMod1_rmin - 1*um" />
-    <constant name="OuterTrackerEndcapPLayer1_rmax"  value="OuterTrackerEndcapPMod1_rmax + 1*um" />
+    <constant name="OuterTrackerEndcapPLayer1_rmin"  value="OuterTrackerEndcapPMod1_rmin" />
+    <constant name="OuterTrackerEndcapPLayer1_rmax"  value="OuterTrackerEndcapPMod1_rmax" />
     <constant name="OuterTrackerEndcapPLayer1_zmin"  value="OuterTrackerEndcapPMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <constant name="OuterTrackerEndcapPMod2_zmin" value="OuterTrackerEndcapP_zmin + 1 * OuterTrackerEndcapP_offset" />
@@ -772,8 +772,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="OuterTrackerEndcapPMod2_x1"    value="2 * OuterTrackerEndcapPMod2_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapPMod2_x2"    value="2 * OuterTrackerEndcapPMod2_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapPMod2_y"     value="OuterTrackerEndcapPMod2_rmax * cos(SiTrackerEndcapMod_angle/2) - OuterTrackerEndcapPMod2_rmin" />
-    <constant name="OuterTrackerEndcapPLayer2_rmin"  value="OuterTrackerEndcapPMod2_rmin - 1*um" />
-    <constant name="OuterTrackerEndcapPLayer2_rmax"  value="OuterTrackerEndcapPMod2_rmax + 1*um" />
+    <constant name="OuterTrackerEndcapPLayer2_rmin"  value="OuterTrackerEndcapPMod2_rmin" />
+    <constant name="OuterTrackerEndcapPLayer2_rmax"  value="OuterTrackerEndcapPMod2_rmax" />
     <constant name="OuterTrackerEndcapPLayer2_zmin"  value="OuterTrackerEndcapPMod2_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <constant name="OuterTrackerEndcapPMod3_zmin" value="OuterTrackerEndcapP_zmin + 2 * OuterTrackerEndcapP_offset" />
@@ -782,8 +782,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="OuterTrackerEndcapPMod3_x1"    value="2 * OuterTrackerEndcapPMod3_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapPMod3_x2"    value="2 * OuterTrackerEndcapPMod3_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapPMod3_y"     value="OuterTrackerEndcapPMod3_rmax * cos(SiTrackerEndcapMod_angle/2) - OuterTrackerEndcapPMod3_rmin" />
-    <constant name="OuterTrackerEndcapPLayer3_rmin"  value="OuterTrackerEndcapPMod3_rmin - 1*um" />
-    <constant name="OuterTrackerEndcapPLayer3_rmax"  value="OuterTrackerEndcapPMod3_rmax + 1*um" />
+    <constant name="OuterTrackerEndcapPLayer3_rmin"  value="OuterTrackerEndcapPMod3_rmin" />
+    <constant name="OuterTrackerEndcapPLayer3_rmax"  value="OuterTrackerEndcapPMod3_rmax" />
     <constant name="OuterTrackerEndcapPLayer3_zmin"  value="OuterTrackerEndcapPMod3_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <comment> The Si tracker endcap ends at position of the last disk </comment>
@@ -800,8 +800,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="OuterTrackerEndcapNMod1_x1"    value="2 * OuterTrackerEndcapNMod1_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapNMod1_x2"    value="2 * OuterTrackerEndcapNMod1_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapNMod1_y"     value="OuterTrackerEndcapNMod1_rmax * cos(SiTrackerEndcapMod_angle/2) - OuterTrackerEndcapNMod1_rmin" />
-    <constant name="OuterTrackerEndcapNLayer1_rmin"  value="OuterTrackerEndcapNMod1_rmin - 1*um" />
-    <constant name="OuterTrackerEndcapNLayer1_rmax"  value="OuterTrackerEndcapNMod1_rmax + 1*um" />
+    <constant name="OuterTrackerEndcapNLayer1_rmin"  value="OuterTrackerEndcapNMod1_rmin" />
+    <constant name="OuterTrackerEndcapNLayer1_rmax"  value="OuterTrackerEndcapNMod1_rmax" />
     <constant name="OuterTrackerEndcapNLayer1_zmin"  value="OuterTrackerEndcapNMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <constant name="OuterTrackerEndcapNMod2_zmin" value="OuterTrackerEndcapN_zmin + 1 * OuterTrackerEndcapN_offset" />
@@ -810,8 +810,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="OuterTrackerEndcapNMod2_x1"    value="2 * OuterTrackerEndcapNMod2_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapNMod2_x2"    value="2 * OuterTrackerEndcapNMod2_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="OuterTrackerEndcapNMod2_y"     value="OuterTrackerEndcapNMod2_rmax * cos(SiTrackerEndcapMod_angle/2) - OuterTrackerEndcapNMod2_rmin" />
-    <constant name="OuterTrackerEndcapNLayer2_rmin"  value="OuterTrackerEndcapNMod2_rmin - 1*um" />
-    <constant name="OuterTrackerEndcapNLayer2_rmax"  value="OuterTrackerEndcapNMod2_rmax + 1*um" />
+    <constant name="OuterTrackerEndcapNLayer2_rmin"  value="OuterTrackerEndcapNMod2_rmin" />
+    <constant name="OuterTrackerEndcapNLayer2_rmax"  value="OuterTrackerEndcapNMod2_rmax" />
     <constant name="OuterTrackerEndcapNLayer2_zmin"  value="OuterTrackerEndcapNMod2_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <comment> The Si tracker endcap ends at position of the last disk </comment>
@@ -973,7 +973,7 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="GEMEndcapMod_dz"                value="GEMEndcapMod_thickness/2 + GEMSpoke_thickness/2" />
     <constant name="GEMEndcapMod_overlap"           value="0" />
     <constant name="GEMEndcapMod_angle"             value="360.0*degree / GEMEndcapMod_count * (1 + GEMEndcapMod_overlap)" />
-    <constant name="GEMEndcapLayer_thickness"       value="GEMEndcapMod_thickness + 2 * GEMEndcapMod_dz + 1*um" />
+    <constant name="GEMEndcapLayer_thickness"       value="GEMEndcapMod_thickness + 2 * GEMEndcapMod_dz" />
 
     <comment> Parameters for the "ring" GEMS around the silicon tracker, which are all identical </comment>
     <constant name="GEMEndcapRingMod_rmin"          value="SiTrackerSupportCyl_rmax + GEMFrameBotEdge_width" />
@@ -993,8 +993,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="GEMEndcapRingModTopFrame_x2"    value="2 * GEMEndcapRingModTopFrame_rmax * sin(GEMEndcapMod_angle/2)" />
     <constant name="GEMEndcapRingModSpoke_length"   value="GEMEndcapRingMod_rmax - GEMEndcapRingModBotFrame_rmax" />
     <constant name="GEMEndcapRingModSpoke_r"        value="(GEMEndcapRingMod_rmax + GEMEndcapRingModBotFrame_rmax)/2" />
-    <constant name="GEMEndcapRingLayer_rmin"        value="GEMEndcapRingModBotFrame_rmin - 1*um" />
-    <constant name="GEMEndcapRingLayer_rmax"        value="GEMEndcapRingModTopFrame_rmax + 1*um" />
+    <constant name="GEMEndcapRingLayer_rmin"        value="GEMEndcapRingModBotFrame_rmin" />
+    <constant name="GEMEndcapRingLayer_rmax"        value="GEMEndcapRingModTopFrame_rmax" />
 
     <comment>
       z position of the "ring" GEMS, note that some are offset slightly
@@ -1031,8 +1031,8 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="GEMEndcapLargeModTopFrame_x2"    value="2 * GEMEndcapLargeModTopFrame_rmax * sin(GEMEndcapMod_angle/2)" />
     <constant name="GEMEndcapLargeModSpoke_length"   value="GEMEndcapLargeMod_rmax - GEMEndcapLargeModBotFrame_rmax" />
     <constant name="GEMEndcapLargeModSpoke_r"        value="(GEMEndcapLargeMod_rmax + GEMEndcapLargeModBotFrame_rmax)/2" />
-    <constant name="GEMEndcapLargeLayer_rmin"        value="GEMEndcapLargeModBotFrame_rmin - 1*um" />
-    <constant name="GEMEndcapLargeLayer_rmax"        value="GEMEndcapLargeModTopFrame_rmax + 1*um" />
+    <constant name="GEMEndcapLargeLayer_rmin"        value="GEMEndcapLargeModBotFrame_rmin" />
+    <constant name="GEMEndcapLargeLayer_rmax"        value="GEMEndcapLargeModTopFrame_rmax" />
 
   </define>
   <detectors>
diff --git a/compact/tracking/silicon_barrel.xml b/compact/tracking/silicon_barrel.xml
index 4fbce770b5..b71747560c 100644
--- a/compact/tracking/silicon_barrel.xml
+++ b/compact/tracking/silicon_barrel.xml
@@ -31,9 +31,9 @@
     <comment> 84cm=2*42cm is the engineer max </comment>
     <constant name="SiBarrelMod2_length"        value="84*cm"/>
 
-    <constant name="SiBarrelLayer1_length"      value="SiBarrelMod1_length + 1*um"/>
-    <constant name="SiBarrelLayer2_length"      value="SiBarrelMod2_length + 1*um"/>
-    <constant name="SiBarrelEnvelope_length"    value="SiBarrelLayer2_length + 1*um" />
+    <constant name="SiBarrelLayer1_length"      value="SiBarrelMod1_length"/>
+    <constant name="SiBarrelLayer2_length"      value="SiBarrelMod2_length"/>
+    <constant name="SiBarrelEnvelope_length"    value="SiBarrelLayer2_length" />
 
     <constant name="SiBarrelLayer_thickness"    value="3.0*cm"/>
     <constant name="SiBarrelLayer1_rmin"        value="SiBarrelMod1_rmin "/>
diff --git a/compact/tracking/silicon_disks.xml b/compact/tracking/silicon_disks.xml
index 94ac075ea6..6c37ba5007 100644
--- a/compact/tracking/silicon_disks.xml
+++ b/compact/tracking/silicon_disks.xml
@@ -28,7 +28,7 @@
     <comment> Global Si endcap variables </comment>
     <constant name="SiTrackerEndcapMod_thickness"   value="SiTrackerEndcapCF_thickness + SiTrackerEndcapAl_thickness + SiTrackerSensor_thickness" />
     <constant name="SiTrackerEndcapMod_angle"       value="360.0*degree / SiTrackerEndcapMod_count * (1 + SiTrackerEndcapMod_overlap)" />
-    <constant name="SiTrackerEndcapLayer_thickness" value="SiTrackerEndcapMod_thickness + 2 * SiTrackerEndcapMod_dz + 1*um" />
+    <constant name="SiTrackerEndcapLayer_thickness" value="SiTrackerEndcapMod_thickness + 2 * SiTrackerEndcapMod_dz" />
 
     <comment> Acts envelope buffer distances </comment>
     <constant name="SiTrackerEndcap_envelope_rmin_delta" value="1*mm"/>
@@ -46,8 +46,8 @@
     <constant name="InnerTrackerEndcapPMod1_x1"     value="2 * InnerTrackerEndcapPMod1_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="InnerTrackerEndcapPMod1_x2"     value="2 * InnerTrackerEndcapPMod1_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="InnerTrackerEndcapPMod1_y"      value="InnerTrackerEndcapPMod1_rmax * cos(SiTrackerEndcapMod_angle/2) - InnerTrackerEndcapPMod1_rmin" />
-    <constant name="InnerTrackerEndcapPLayer1_rmin" value="InnerTrackerEndcapPMod1_rmin - 1*um" />
-    <constant name="InnerTrackerEndcapPLayer1_rmax" value="InnerTrackerEndcapPMod1_rmax + 1*um" />
+    <constant name="InnerTrackerEndcapPLayer1_rmin" value="InnerTrackerEndcapPMod1_rmin" />
+    <constant name="InnerTrackerEndcapPLayer1_rmax" value="InnerTrackerEndcapPMod1_rmax" />
     <constant name="InnerTrackerEndcapPLayer1_zmin" value="InnerTrackerEndcapPMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <constant name="InnerTrackerEndcapNMod1_zmin"   value="InnerTrackerEndcapN_zmin" />
@@ -56,8 +56,8 @@
     <constant name="InnerTrackerEndcapNMod1_x1"     value="2 * InnerTrackerEndcapNMod1_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="InnerTrackerEndcapNMod1_x2"     value="2 * InnerTrackerEndcapNMod1_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="InnerTrackerEndcapNMod1_y"      value="InnerTrackerEndcapNMod1_rmax * cos(SiTrackerEndcapMod_angle/2) - InnerTrackerEndcapNMod1_rmin" />
-    <constant name="InnerTrackerEndcapNLayer1_rmin" value="InnerTrackerEndcapNMod1_rmin - 1*um" />
-    <constant name="InnerTrackerEndcapNLayer1_rmax" value="InnerTrackerEndcapNMod1_rmax + 1*um" />
+    <constant name="InnerTrackerEndcapNLayer1_rmin" value="InnerTrackerEndcapNMod1_rmin" />
+    <constant name="InnerTrackerEndcapNLayer1_rmax" value="InnerTrackerEndcapNMod1_rmax" />
     <constant name="InnerTrackerEndcapNLayer1_zmin" value="InnerTrackerEndcapNMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
   </define>
   <detectors>
@@ -134,8 +134,8 @@
     <constant name="TrackerEndcapPMod1_x1"     value="2 * TrackerEndcapPMod1_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapPMod1_x2"     value="2 * TrackerEndcapPMod1_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapPMod1_y"      value="TrackerEndcapPMod1_rmax * cos(SiTrackerEndcapMod_angle/2) - TrackerEndcapPMod1_rmin" />
-    <constant name="TrackerEndcapPLayer1_rmin" value="TrackerEndcapPMod1_rmin - 1*um" />
-    <constant name="TrackerEndcapPLayer1_rmax" value="TrackerEndcapPMod1_rmax + 1*um" />
+    <constant name="TrackerEndcapPLayer1_rmin" value="TrackerEndcapPMod1_rmin" />
+    <constant name="TrackerEndcapPLayer1_rmax" value="TrackerEndcapPMod1_rmax" />
     <constant name="TrackerEndcapPLayer1_zmin" value="TrackerEndcapPMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
     <constant name="TrackerEndcapPMod2_zmin"   value="TrackerEndcapPDisk2_zmin" />
     <constant name="TrackerEndcapPMod2_rmin"   value="TrackerEndcapPDisk2_rmin" />
@@ -143,8 +143,8 @@
     <constant name="TrackerEndcapPMod2_x1"     value="2 * TrackerEndcapPMod2_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapPMod2_x2"     value="2 * TrackerEndcapPMod2_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapPMod2_y"      value="TrackerEndcapPMod2_rmax * cos(SiTrackerEndcapMod_angle/2) - TrackerEndcapPMod2_rmin" />
-    <constant name="TrackerEndcapPLayer2_rmin" value="TrackerEndcapPMod2_rmin - 1*um" />
-    <constant name="TrackerEndcapPLayer2_rmax" value="TrackerEndcapPMod2_rmax + 1*um" />
+    <constant name="TrackerEndcapPLayer2_rmin" value="TrackerEndcapPMod2_rmin" />
+    <constant name="TrackerEndcapPLayer2_rmax" value="TrackerEndcapPMod2_rmax" />
     <constant name="TrackerEndcapPLayer2_zmin" value="TrackerEndcapPMod2_zmin - SiTrackerEndcapLayer_thickness/2" />
     <constant name="TrackerEndcapPMod3_zmin"   value="TrackerEndcapPDisk3_zmin" />
     <constant name="TrackerEndcapPMod3_rmin"   value="TrackerEndcapPDisk3_rmin" />
@@ -152,8 +152,8 @@
     <constant name="TrackerEndcapPMod3_x1"     value="2 * TrackerEndcapPMod3_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapPMod3_x2"     value="2 * TrackerEndcapPMod3_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapPMod3_y"      value="TrackerEndcapPMod3_rmax * cos(SiTrackerEndcapMod_angle/2) - TrackerEndcapPMod3_rmin" />
-    <constant name="TrackerEndcapPLayer3_rmin" value="TrackerEndcapPMod3_rmin - 1*um" />
-    <constant name="TrackerEndcapPLayer3_rmax" value="TrackerEndcapPMod3_rmax + 1*um" />
+    <constant name="TrackerEndcapPLayer3_rmin" value="TrackerEndcapPMod3_rmin" />
+    <constant name="TrackerEndcapPLayer3_rmax" value="TrackerEndcapPMod3_rmax" />
     <constant name="TrackerEndcapPLayer3_zmin" value="TrackerEndcapPMod3_zmin - SiTrackerEndcapLayer_thickness/2" />
     <constant name="TrackerEndcapPMod4_zmin"   value="TrackerEndcapPDisk4_zmin" />
     <constant name="TrackerEndcapPMod4_rmin"   value="TrackerEndcapPDisk4_rmin" />
@@ -161,8 +161,8 @@
     <constant name="TrackerEndcapPMod4_x1"     value="2 * TrackerEndcapPMod4_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapPMod4_x2"     value="2 * TrackerEndcapPMod4_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapPMod4_y"      value="TrackerEndcapPMod4_rmax * cos(SiTrackerEndcapMod_angle/2) - TrackerEndcapPMod4_rmin" />
-    <constant name="TrackerEndcapPLayer4_rmin" value="TrackerEndcapPMod4_rmin - 1*um" />
-    <constant name="TrackerEndcapPLayer4_rmax" value="TrackerEndcapPMod4_rmax + 1*um" />
+    <constant name="TrackerEndcapPLayer4_rmin" value="TrackerEndcapPMod4_rmin" />
+    <constant name="TrackerEndcapPLayer4_rmax" value="TrackerEndcapPMod4_rmax" />
     <constant name="TrackerEndcapPLayer4_zmin" value="TrackerEndcapPMod4_zmin - SiTrackerEndcapLayer_thickness/2" />
 
     <constant name="TrackerEndcapNMod1_zmin"   value="TrackerEndcapNDisk1_zmin" />
@@ -171,8 +171,8 @@
     <constant name="TrackerEndcapNMod1_x1"     value="2 * TrackerEndcapNMod1_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapNMod1_x2"     value="2 * TrackerEndcapNMod1_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapNMod1_y"      value="TrackerEndcapNMod1_rmax * cos(SiTrackerEndcapMod_angle/2) - TrackerEndcapNMod1_rmin" />
-    <constant name="TrackerEndcapNLayer1_rmin" value="TrackerEndcapNMod1_rmin - 1*um" />
-    <constant name="TrackerEndcapNLayer1_rmax" value="TrackerEndcapNMod1_rmax + 1*um" />
+    <constant name="TrackerEndcapNLayer1_rmin" value="TrackerEndcapNMod1_rmin" />
+    <constant name="TrackerEndcapNLayer1_rmax" value="TrackerEndcapNMod1_rmax" />
     <constant name="TrackerEndcapNLayer1_zmin" value="TrackerEndcapNMod1_zmin - SiTrackerEndcapLayer_thickness/2" />
     <constant name="TrackerEndcapNMod2_zmin"   value="TrackerEndcapNDisk2_zmin" />
     <constant name="TrackerEndcapNMod2_rmin"   value="TrackerEndcapNDisk2_rmin" />
@@ -180,8 +180,8 @@
     <constant name="TrackerEndcapNMod2_x1"     value="2 * TrackerEndcapNMod2_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapNMod2_x2"     value="2 * TrackerEndcapNMod2_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapNMod2_y"      value="TrackerEndcapNMod2_rmax * cos(SiTrackerEndcapMod_angle/2) - TrackerEndcapNMod2_rmin" />
-    <constant name="TrackerEndcapNLayer2_rmin" value="TrackerEndcapNMod2_rmin - 1*um" />
-    <constant name="TrackerEndcapNLayer2_rmax" value="TrackerEndcapNMod2_rmax + 1*um" />
+    <constant name="TrackerEndcapNLayer2_rmin" value="TrackerEndcapNMod2_rmin" />
+    <constant name="TrackerEndcapNLayer2_rmax" value="TrackerEndcapNMod2_rmax" />
     <constant name="TrackerEndcapNLayer2_zmin" value="TrackerEndcapNMod2_zmin - SiTrackerEndcapLayer_thickness/2" />
     <constant name="TrackerEndcapNMod3_zmin"   value="TrackerEndcapNDisk3_zmin" />
     <constant name="TrackerEndcapNMod3_rmin"   value="TrackerEndcapNDisk3_rmin" />
@@ -189,8 +189,8 @@
     <constant name="TrackerEndcapNMod3_x1"     value="2 * TrackerEndcapNMod3_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapNMod3_x2"     value="2 * TrackerEndcapNMod3_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapNMod3_y"      value="TrackerEndcapNMod3_rmax * cos(SiTrackerEndcapMod_angle/2) - TrackerEndcapNMod3_rmin" />
-    <constant name="TrackerEndcapNLayer3_rmin" value="TrackerEndcapNMod3_rmin - 1*um" />
-    <constant name="TrackerEndcapNLayer3_rmax" value="TrackerEndcapNMod3_rmax + 1*um" />
+    <constant name="TrackerEndcapNLayer3_rmin" value="TrackerEndcapNMod3_rmin" />
+    <constant name="TrackerEndcapNLayer3_rmax" value="TrackerEndcapNMod3_rmax" />
     <constant name="TrackerEndcapNLayer3_zmin" value="TrackerEndcapNMod3_zmin - SiTrackerEndcapLayer_thickness/2" />
     <commnet> symmetric N and P disks (5 each)</commnet>
     <constant name="TrackerEndcapNMod4_zmin"   value="TrackerEndcapNDisk4_zmin" />
@@ -199,8 +199,8 @@
     <constant name="TrackerEndcapNMod4_x1"     value="2 * TrackerEndcapNMod4_rmin * tan(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapNMod4_x2"     value="2 * TrackerEndcapNMod4_rmax * sin(SiTrackerEndcapMod_angle/2)" />
     <constant name="TrackerEndcapNMod4_y"      value="TrackerEndcapNMod4_rmax * cos(SiTrackerEndcapMod_angle/2) - TrackerEndcapNMod4_rmin" />
-    <constant name="TrackerEndcapNLayer4_rmin" value="TrackerEndcapNMod4_rmin - 1*um" />
-    <constant name="TrackerEndcapNLayer4_rmax" value="TrackerEndcapNMod4_rmax + 1*um" />
+    <constant name="TrackerEndcapNLayer4_rmin" value="TrackerEndcapNMod4_rmin" />
+    <constant name="TrackerEndcapNLayer4_rmax" value="TrackerEndcapNMod4_rmax" />
     <constant name="TrackerEndcapNLayer4_zmin" value="TrackerEndcapNMod4_zmin - SiTrackerEndcapLayer_thickness/2" />
 
   </define>
diff --git a/compact/tracking/tof_endcap.xml b/compact/tracking/tof_endcap.xml
index 7ee623b249..0988b0fabb 100644
--- a/compact/tracking/tof_endcap.xml
+++ b/compact/tracking/tof_endcap.xml
@@ -107,8 +107,8 @@
     <constant name="ForwardTOFMod_rmax"         value="ForwardTOFRegion_maxR" />
     <constant name="ForwardTOFMod1_zmin"        value="ForwardTOF_zmin" />
     <constant name="ForwardTOFMod2_zmin"        value="ForwardTOF_zmin + ForwardTOFMod_offset" />
-    <constant name="ForwardTOFLayer_rmin"       value="ForwardTOFMod_rmin - 1*um" />
-    <constant name="ForwardTOFLayer_rmax"       value="ForwardTOFMod_rmax + 1*um" />
+    <constant name="ForwardTOFLayer_rmin"       value="ForwardTOFMod_rmin" />
+    <constant name="ForwardTOFLayer_rmax"       value="ForwardTOFMod_rmax" />
     <constant name="ForwardTOFLayer1_zmin"      value="ForwardTOFMod1_zmin - TOFEndcapLayer_thickness / 2" />
     <constant name="ForwardTOFLayer2_zmin"      value="ForwardTOFMod2_zmin - TOFEndcapLayer_thickness / 2" />
 
diff --git a/compact/tracking/vertex_barrel.xml b/compact/tracking/vertex_barrel.xml
index f2fc4ad20b..9c7395c0ff 100644
--- a/compact/tracking/vertex_barrel.xml
+++ b/compact/tracking/vertex_barrel.xml
@@ -27,7 +27,7 @@
     </documentation>
 
     <constant name="VertexBarrelEnvelope_length"    value="VertexTrackingRegion_length"/>
-    <constant name="VertexBarrelLayer_length"       value="VertexBarrelMod_length + 1*um"/>
+    <constant name="VertexBarrelLayer_length"       value="VertexBarrelMod_length"/>
 
     <constant name="VertexBarrelLayer_thickness"    value="0.2*cm"/>
     <constant name="VertexBarrelMod_thickness"      value="0.1*cm"/>
diff --git a/src/magnetVacuumFF.cpp b/src/magnetVacuumFF.cpp
index 2f26763206..7f924778d2 100644
--- a/src/magnetVacuumFF.cpp
+++ b/src/magnetVacuumFF.cpp
@@ -99,6 +99,9 @@ static Ref_t create_detector(Detector& det, xml_h e, SensitiveDetector /* sens *
     z_elem_magnet.push_back(pos_z * dd4hep::cm);
   }
 
+  xml_comp_t x_end_of_the_world = x_det.child(_Unicode(end_of_the_world));
+  double end_of_the_world_z     = x_end_of_the_world.attr<double>(_Unicode(z));
+
   int numMagnets = radii_magnet.size(); //number of actual FF magnets between IP and FF detectors
   int numGaps =
       numMagnets -
@@ -265,7 +268,7 @@ static Ref_t create_detector(Detector& det, xml_h e, SensitiveDetector /* sens *
 
     int pieceIdx           = numMagnets - 1; // last B2PF magnet
     std::string piece_name = Form("GapVacuum%d", numGaps + numMagnets + 1);
-    double endGapLength    = (10000.0 - z_end[pieceIdx]) / cos(rotation_magnet[pieceIdx]);
+    double endGapLength = (end_of_the_world_z - z_end[pieceIdx]) / cos(rotation_magnet[pieceIdx]);
     endGapLength =
         endGapLength -
         4 * radii_magnet[pieceIdx] *
diff --git a/templates/epic.xml.jinja2 b/templates/epic.xml.jinja2
index 687347a0e4..107c2836b9 100644
--- a/templates/epic.xml.jinja2
+++ b/templates/epic.xml.jinja2
@@ -93,10 +93,18 @@
   <documentation level="0">
     ## World Volume
 
-    The world is a simple box, but could be a union of multiple regions.
+    The world is a union of multiple regions.
   </documentation>
   <world material="Air">
-    <shape type="Box" dx="world_dx" dy="world_dy" dz="world_dz"/>
+    <shape type="BooleanShape" operation="Union">
+      <shape type="BooleanShape" operation="Union">
+        <shape type="Box" dx="exp_hall_dx" dy="exp_hall_dy" dz="exp_hall_dz"/>
+        <shape type="Box" dx="backward_dx" dy="backward_dy" dz="backward_dz"/>
+        <position x="backward_x0" y="0*cm" z="- exp_hall_dz - backward_dz"/>
+      </shape>
+      <shape type="Box" dx="forward_dx" dy="forward_dy" dz="forward_dz"/>
+      <position x="forward_x0" y="0*cm" z="+ exp_hall_dz + forward_dz"/>
+    </shape>
     <!--regionref   name="world_region"/-->
     <!--limitsetref name="world_limits"/-->
   </world>