I'm looking at building up a frame I have with a clamp-on Campagnolo front derailleur. The ones that I've seen for sale have a clamp diameter that seems to be incompatible with my frame (am I correct in thinking this has to equal seat tube diameter?). However, there is a shimano FD clamp already attached to the frame.
Would it be possible to just attach a campy braze-on or clamp-on (with the clamp itself removed) FD directly to this? Or do I have to try my luck searching for a derailleur with the right clamp diameter? I can provide a picture of the Shimano clamp if that'll help