Out of curiosity, I "held" my 10-22 against the mount of my 5D to see at what point it would stop vignetting. 16mm. I would imagine less so, if it was properly mounted. I would be curious to try it on a FF without destroying my mirror.
Is here a quick and reversible mod that could be done to the 10-22, so it does mount on a 5D and clear thr mirror ?