On what band? Am/FM/DSM? If the antenna is outside and above all the paint I would think on 2.4 you would be fine. Carbon fiber on the other hand can cause issues with RF.
I used House of Kolors metal flake on my Pay n Pak. I didn't have any problems on 2.4 DSM. The one thing I did notice was, the coax tip of the antenna needs to be vertical to remain omni-directional. If you lay the tip down in the box, when it lines up with your transmitter, it will loose signal.
I have got an Ossi F1 painted in red metal flake and the 2.4 antenna is under the cowling, I also have a vee bottom painted in Gold metal flake and the 2.4 antenna is mounted on top of the sloping dash board and i have no troubles with either boats.