I am currently in the midst of permanently modifying my Kodak 3A to take 120 film when I started thinking about that metal ridge. Has anyone filed/ground down the metal ridge which appears (when looking in from the back of the camera through the bellows and out the lens) before the bellows do? It looks that each side ~1/4" wide so if you ground this away you would add about ~1/2" in width which would give you ~6x17cm negatives. I'm definitely going to try this as it will also make it easier to use the frame numbers to delineate where to stop advancing the film (use the same system as with the 6x17 LF backs from China). Right now I have a 135mm Graflex Optar mounted on mine, but I can switch this out for a 90mm angulon if I need the wider angle, or a 180mm RR if I need a smaller angle of view. What do you have mounted on yours?