Fiberglass is not fireproof, it will burn, but so will the plastic pieces. Do not have the glass in a major bind because it will try to warp under heat to relieve its stress, thats how I made fitment modifications to the last kit I installed. Mix your resin a little on the cold side and it will not be so prone to crack due to vibration, and be EXTREMELY careful drilling it, use a small pilot bit and stage larger in small steps. My 2 cents.
Fiberglass IS NOT flammable, the resin and the hardending compound and the cloth, IS flammable, but when you complete the mixture, the chemical compound changes, and is no longer flammable.
I cannot find properties of fiberglass on the net, if anyone can please confirm this for me, thank you!