The polyester resin gelcoat is non-structural. It protects the
underlying laminate resin and PVC core from excess temperatures and
the laminate resin (Usually epoxy) from UV exposure.

Structures that are bonded with an adhesive resin have a different
failure mode, and expoxy adhesive resins usually have a higher TG than
laminate resins

Read and follow the POH and AMM of the particular aircraft in
question. Most prohibit dark markings some areas.

aerodyne