My wife just bought a used Ultegra 6600 gruppo to upgrade her old mixed components, the problem was the front deraileur's clamp is 34.9 and her frame's seattube dia is 31.8 so it's quite loose.

My question is, aside from shimming the clamp to fit, is it possible to just buy a 31.8 braze on clamp then screw off the FD-6603 from the clamp it comes with and put it on the newbraze on clamp?

Or any easier solutions you could suggest? Thanks!