[cody]

Looks like epoxy is the way to go. I just did some quick googling.

http://www.airfieldmodels.com/inform.../adhesives.htm

Fuel-proof

Fuel should not be able to get inside the airframe and fuel-proofness is not much of a consideration for general construction. Fuel tanks can and do split open from improper assembly, defective molding or design or a crash. The fuel compartment should definitely be coated with something fuel proof such as epoxy or polyurethane (paint). Joints around the firewall should also be glued with a fuel-proof glue.

http://www.rcrcc.com/adhesive_reference_chart.htm

Epoxy -- This is a two part glue which is sold with various cure times and formulations. The two parts must be mixed to cause a cure. As a rule, generally faster curing epoxies tend to become brittle with time. Slow curing epoxy, in contrast, will tend to remain fairly flexible. Use this glue in all high stress areas such as attaching the firewall, landing gear blocks and tail feathers. Commercially available examples include the Hobbypoxy lineup as well as everybody else's house brands. It can be easily cleaned up with alcohol before it cures and is often thinned with alcohol and painted into engine bays and fuel compartments to help fuel-proof the plane. Smart people do this and recommend to all other modellers that they should also do this. Stupid people don't, and eventually their engine flies off with the firewall, leaving the plane behind. I was stupid once. God I hate fuel creep!