Now we see through a glass, darkly...
- Apr 5, 2016
It's not doable because the throat diameter of the RF mount is much larger than the throat diameter of the EF-M mount and the lugs on RF lenses protrude more than 2mm behind the flange plate.Excellent News.
I wonder if Canon will make an R - M lens adapter. It should be doable since the M Flange focal distance is 18mm, and the R is 20mm.
My guess is that they will make one soon.