Texture Coordinates for VR PPE Material

I am trying to perturb the screen space coordinates of the postprocess input with a normal map in a blendable pp material like so:

And it works!

The problem is that I’m trying to do this for VR. I end up getting image doubling in the headset (works fine on monitor). The problem seems to be coming from the ScreenAligned UVs node. Without that plugged in, everything works fine in the headset. Plugging that node into the SceneTexture’s UVs results in image doubling (even without perturbing).

Is there some additional math I need to do to my ScreenAligned UVs for use in VR?