Rodney

Over thirty years of building and flying RC, I have found it always pays to fuelproof the inside of the fuselage if you plan to keep the airplane for a long time. Sooner or later, I don't care how good the tank is, you will get a fuel spill inside the plane. Not only do I fuelproof the inside, I also am one who drills a hole in an appropreate spot to drain any gross fuel leak out the bottom of the plane. This gaurds against that time when the fuel line breaks at the tank mouth or similar problems and your refueling proceedure pumps a few extra ounces into the bottom of the fuselage. The added weight, even if you use epoxy is muniscal, probably much less than 2 ounces. The epoxy serves a second purpose, it greatly strengthens any joints in that area, especially firewall to fuselage.