On the subject of fuelproofing I offer a warning that came in my SIG Sumthi' Extra kit. "Don't fuelproof anywhere that will be covered on the other side before covering." In other words, do the covering job then fuelproof the other side of the strusture. They claim that the covering won't adhere to an area thet has had its other side coated with a sealer like epoxy or any other fuel proofing product. The reason is that the balsa needs to breath through to the other side and cannot do that if the other side is sealed. So cover first, then fuelproof.