The surgery was a success!! Before, I couldn't even mount the lens because the fin would catch on the plastic mirror housing. Now, it works perfectly right up to infinity where the mirror will hang in portrait orientation. I think a thicker adapter will solve this. I am not worried about needing this particular lens at infinity anyway.
I will post pics of the after surgery scars and some samples from the lens tomorrow. Now I am off to bed to sleep without worry
Rachp; I can see if I still have my Contax adapter in the bag; it is the same adapter I used for my 60 on the 5D and it worked flawlessly. I won't be using it.
The fin is present on a few on the old CY lens line up. I had both the 60 S-Planar, and the 85/1.2 50th, and it was on both. On my body, with the adapters I had, it cleared just enough while making a slight groove in my Canon mirror box right above the electrical contacts. I believe it was made into lenses that were heavier or longer (as in the case of a fully extended macro) to keep the lens from "drooping" off plane. The first editions of CY mount was always a point of criticism amongst camera techies as it seemed to be a bit under engineered when compared to other manufacturers designs. The construction of the mount did change as the lens line up evolved, but I am not sure if the fin on those few were ever eliminated or not.
That makes sense because this lens is definitely the heaviest CY I have ever used! I got the same catch on my mirror box but mine wouldn't go any further. I think I do need a little thicker adapter. I love the lens - great Zeiss colors and look. I have only been able to snap a few test shots while sitting behind my desk - crappy lighting and no interesting subjects Maybe I can sneak outside today and give it a try!