Acouple of things... Someone posted a long time ago how to take the front piece off a trashed rb body and mount it on a lens board to use with rb lens. The trick is toget the cocking of the shutter correct. I have the front piece, just never got aroundtoit so it's just another project.
I have no idea of coverage. Some claims seem a bit outrageous.
The rb backs will fit a Grafex back. I have used it on my 2x3 Speed. But ya know... I think the film plane offset is just not quite correct. The negatives are a bit..soft.
tim in san jose