Doremus Scudder,

I'll know for sure what the orientation will be once I take delivery of the ground glass pair. From what I can see the glass is nothing more than a protective cover for the fresnel screen, the screen being the focusing aid. As long as the focusing aid is on the true focus plane one shouldn't have any issues. I've noticed on one YouTube video https://www.youtube.com/watch?v=CVpveOEk-I0&t=513s that this guy apparently has a combination where both the ground glass and the fresnel screen were the focusing aids hence his need to install both of them from opposite sides of the holder allowing each to share the same focus plane. That's something I don't want to do.

It sounds like you are right with the Wista ground glass combination. I wouldn't know as I haven't seen one.