Looking for info on converting a Contax 645 MFB-1B film magazine insert (for 220 film) to use with 120 film. I have the 220 Magazine and it will shoot with 120 film in it but does not rewind after 16 images. I've seen anecdotes about "converting" the 220 magazines to use w/ 120 film, but haven't found any more info on how it's done or if it solves the rewind issue. Seeing as these cameras are no longer made I hate to toss the 220 insert just because 220 film was discontinued. Has anyone ever successfully converted one? Thanks!