Hi Thierry
Shimano supplies a small adhesive-backed plate with their Di2 FDs for you to put on the frame for this purpose. I would not recommend running that setscrew directly into the carbon. Personally, I've never found the need to use the setscrew to clean up the shifting, but I get the principle they're driving at. Relying only on the FD clamp-up may be sufficient when we're talking about aluminum FD hangers, and in truth that's the only style I've ever had my Di2 mounted on, but for carbon it's possible you need that extra support. Suggest you locate that Shimano-supplied plate and install it and see what happens.
Carl Matson
Shimano supplies a small adhesive-backed plate with their Di2 FDs for you to put on the frame for this purpose. I would not recommend running that setscrew directly into the carbon. Personally, I've never found the need to use the setscrew to clean up the shifting, but I get the principle they're driving at. Relying only on the FD clamp-up may be sufficient when we're talking about aluminum FD hangers, and in truth that's the only style I've ever had my Di2 mounted on, but for carbon it's possible you need that extra support. Suggest you locate that Shimano-supplied plate and install it and see what happens.
Carl Matson