I tried running both on standard 1280×1024/1600×1200 and 1080×1200 resolutions, and yes I have a custom resoluton defined in Nvidia settings. Game still crashes with vorpx.
I have even tried to run it on everything on low settings and still no luck.
The only recommendation I can give you is to set up a custom 1080×1200 resolution in nvidia settings.
As strange as it may sound game looks better in this resolution + some anti-aliasing 2x,4x,8x) than in for example 1600×1200.
That is probably because 1080×1200 is the rift’s native resolution and things aren’t as blurry as they are in other resolutions. Additionally in 1080×1200 it runs considerably smoother than in other resolutions I have tested.
The only problem right now is for vorpx to save settings across restarts.
Try creating a custom resolution in your nvidia settings (1080:1200)
Then edit skyrimprefs.ini file located in my games (C drive) to set that resolution in game (if the launcher would not allow you to pick this one)
1080×1200 is a 1:1 rift resolution so everything looks way better than on 1280×1024 or 1600×1200 resolutions and it works a lot faster.
If aliasing is a problem you can always set some antialiasing (x2,x4,x8) to make it look better.
It should help a lot with fps.
Additionally you can use one of the Z-buffer modes (ok&save + game restart required to take effect)