many CF bikes will never accept any kind of clamp-on FD as the seat tubes are such weird shapes down there. they have a FD mount that is riveted or screwed onto the frame instead, and take the FD designed for brazed on mounts, of course.

another point has been pointed out above: you need to be careful not to strangle the carbon tube, but the carbon seattubes are fairly strong in compression so they can use a clamp-on type if the tube shape allows it.