I don't know if this has been fixed as I'm still on build 29.0.19, sorry if it is.
There seems to be a minor bug when using madVR. It seems the scailing or the zoom plays up when going fullscreen from windowed mode on every first launch and playback. You can see it in the madVR OSD next to touch window from inside, it says something like "align center top".
Fixable by exiting fullscreen and entering again.
Furthermore, it only affects uncropped content, its no biggie if you're not cropping black bars but if you are it shifts the image. I don't know if this has any affect on JRVR though, but yeah like I said, fixable by exiting and re-entering fullscreen.
Thanks guys for the great work you've put in throughout the years. God bless.