Hi Michael,
"I wish that Austin would comment on your assertion that the YC/MM lenses s/b able to handle w/o problem a full frame sensor."
It is a fact, that the CY lense mount is narrow, and a wider mount would be necessary to avoid severe falloff when using wide angle lenses without the use of microprisms. Microprisms work OK, but they are not the same as not using microprisms. There were many other reasons to change the CY mount to the new N mount, one very compelling one is simply electronics, for both autofocus and lense information (aperture chosen, min aperture and even focal length for zoom lenses).
"the technical reasons that this is impossible."
Not impossible, but would allow severe falloff with wide angle lenses...starting at about 28mm would be my guess. There are solutions to this that don't require larger exit pupils, one is simply using gain on the periphery, but this has the effect of exacerbating noise, so that, IMO, isn't the best choice. Second is redesigning the lense to allow more perpendicular rays...but I'm not sure how this effects overall image quality when you do it with a smaller exit pupil. Another is to reduce the well depth of the sensor, but that can only be reduced so far, and, unfortunately, you are limited by what manufacturers and technology offer. And another is to use microprisms to re-align the light rays so they are more perpendicular, but this does in fact introduct some degredation into the image, but how much is really open for discussion and I have not analyzed it at all. My first choice would be widening the lense mount to allow for lenses to be designed to have a more perpendicular exit pupil.
Regards,
Austin