So I just got my new H4D-50, and want to use the back on my Linhof Techno with a Phase One H 101 adapter plate, the same plate I'm using for my H-mount Aptus back.
Unfortunately the H4D-50 back does not fit on the adapter plate. It's hard to see exactly where it collides, but I have a theory. The safety catch button on top of the back collides with the release button on the adapter plate housing. It fits under it still and it does not seem to be that which holds it off (but rather a misaligned light-trap or peg feature of the plate), but I'm thinking that it forces down the back in a too low position forcing the other features out of alignment.
Looking at pictures of older Hassy gear it seems like they did not have this safety catch button, and I'm guessing that my adapter plate was manufactured at that time. Another theory is that the plate is not up to spec, which would be scandal for a $500 plate...
I've attached pictures of the safety catch button and the release housing of the plate. I've started to sand it down to make space, but I need to get a better tool.
I thought I'd ask here and see if anyone has come across this problem before and know the reason, and if my theory is correct. Guesses are welcome too :-)