Not quite sure but I think the thing you describe will mess up the focal plane of where the lens meets the film, and you'll have to re-do the focus knob to adjust for this change (if that's even possible). Or am I reading incorrectly.
I ran into this issue when I tried adding a CB-70 onto my RZ67... FAIL lol!!
I still have the CB-70 yours for $250! Lol (I know... Broke... Me too that's why I'm selling at cost).
Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1, 5DmkII / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic | Sent w/ iPhone using Tapatalk