I always fuel proof (with epoxy thinned with heat) the firewall, engine compartment, and the fuel compartment too. Do this because I have lost a plane because of a fuel leak. Ultra Sport 60 that I didn't fuel proof the fuel compartment. It had a fuel leak from the tank that I didn't notice because the wood was soaking it up. The fuel weakened the glue joint for the F2 former, and this former held the dowels on the front of the wing and held the wing in place. During an outside loop the former pulled out, and of course the wing separated from the fuselage. Wing floated down and landed softly in the top of a mesquite tree, but the fuselage became a lawn dart and was totalled.

Hope this helps

Ken