I'm helping a friend build up an S-Works Crux (essentially the old S-Works TriCross frame) from the module (frame/crank) up. We're using Ultegra 6700 with the chainrings that came on the frame from Specialized -- 46T/34T.
When I adjust the position of the front derailleur so it's close enough to the chainring the back end of the derailleur cage is very close to the chainstay (see pictures -- the clearance is less than 1 mm). He and I have discussed it and think we have two options -- move the FD up a little bit and maybe compromise shift performance, or replace the chainrings with a 50/34 set, which would require moving the derailleur up a bit.
I'm trying to decide if this is going to be a problem that will need to be addressed before the bike is ever ridden. Obviously it'll be far enough away when he's riding on the 46T ring but I'm concerned if the clearance is enough for any movement/deflection of the chainstay or derailleur.