FSR4 in Cities Skylines 2

[AdvancedFollower]

Does anyone know of a reliable method to get FSR4 working in Cities Skylines 2? I've tried the 3 options below, but they each have serious issues.

If you choose FSR3.x and FSR 3.1.2 in Optiscaler and enable FSR4 override in Adrenaline, the initial Adrenaline popup in the upper right corner shows FSR4 is enabled. However once you're in the game, if you hit Alt+R to open the Adrenaline overlay, it says FSR4 is not enabled. This can also be confirmed by visually inspecting the image quality, which shows it's clearly using FSR3.

Enabling FSR3/4 w.DX12 in Optiscaler works fine during normal gameplay and looks significantly better than FSR3. However if you try to save your game, either a quicksave or by opening the Save menu, the game instantly crashes to the desktop and the following crash is logged:
ExceptionAddress: 00007fffea9b8728 (D3D12Core!CCommandQueue<0>::Signal+0x0000000000000078)
ExceptionCode: c0000005 (Access violation)

If you run the game with "-force-d3d12", the FSR3/4 DX12 mode works and doesn't crash, but forcing DX12 reduces the framerate by ~50% and the GPU usage by a similar amount.

System:
Ryzen 5950X, 32 GB RAM, Radeon RX 9070 XT, Windows 11, 25.10.2 drivers, latest version of Optiscaler and Cities Skylines 2.