Yes agree - simple enough to try some adapters to try them out as EF mount. But what is the reason this is popular? Why not just use them with a Nikon mount? The only reason I can see is because one might already have a EF mount on the camera and/or an EF speedbooster etc. Other then that I cant see why.

The Mamiya's are designed for 6x4.5 image circle - not sure how much beyond this they project but its probably safe to say out to 70mm at least. The Mamiya APO's are quite something - very high end medium format glass. I bought them for my Alpa FPS12 camera.

I have the Mamiya adapter for the Alpa but there is also a PL mount adapter for the ALPA. I never intend to use these Mamiya's with a Mamiya camera - only ever on the Alpa camera. So nothing lost by converting the Mamiya's to PL since I will use the Alpa PL adapter to the Alpa FPS12. But this approach opens these expensive lenses up to using them on an S35 or bigger cinema camera. I agree they are not really suited to the S16 chip, but an interesting tool in the box nonetheless. I do get I may only use them on S16 once in a blue moon. It would surely be interesting to test them out to see what they do resolve on S16 4K - the FOV would be tiny and using only the very very center of the glass. It may be a way to get in really close for a tight head shot on a big cat ?? But it may be way too soft as well.

I do expect that one day in the future that 8K will be a thing at the BM level and thats where these big lenses will shine.

I PM'd you re the PL to M43.