Thanks Chris, I am about to go play with it a bit and see what I get. For the record, my M3 with a 50mm is pretty darn a accurate in terms of representing the actual image area with the frame lines.
I am only really concerned with these variances at landscape distances, I would hate to keep cropping off some 10-15% of precious neg space consistently.
As aside, the differences in size between the Mamiya lenses and Hassy CF lenses is huge, that 50mm is nice and small!