A decent carbon frame will be reinforced slightly (or not need it) where the maker expects you to clamp on a front derailleur. But be aware that it's possible to damage the tube by over tightening or with a badly formed rigid clamp body.
Fit the FD around the tube and close the clamp with your fingers. It should fit right and close finger tight without digging in anyplace. Some may need a bit of flex for the curves to match, but if it needs more that a light touch, the clamp will distort the tube when tightened and crack it. Also check mfr. torque specs, or if none are available tighten only as tight as needed for the FD to do it's job. I paint a bit of traction compound inside the clamp to increase friction and lower the needed clamping force.
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