Answer
There have been an unusually large number of questions asked in the forum recently if some type of fiber reinforced plastic material can be used in the structure of a Regular class aircraft in a certain way.
The answer is always no. Teams are not allowed to use carbon fiber tube, carbon fiber rod, carbon fiber layups, fiberglass rods, fiberglass tubes, fiberglass layups, pre-cured composite sheet or shaped material of any kind, fiberglass, Kevlar or any other type of fiber reinforced plastic not listed here in the structure of the Regular class aircraft
The sole exceptions are non-structural commercially available FRP hardware items listed in the rules: motor mount, prop, landing gear, and control linkage components.