I've been reading a lot about spraymax as a fuelproof clearcoat over other spray paints.
A fuel proof clear coat is great.
The only problem is that your under coats (primer, color coats) usually arent fuel proof. If you take the primer and color coats all the way to your fuel filler opening, the gas will/may/could react with the coats that aren't fuel proof.
The trick is to seal the under coats in with the fuel proof clear so the gas won't come in contact with them.
Tape up the fuel filler about 1/4 inch from the opening and prime. Sand and when you go to put the color coat on, move the tape line up about 1/8 of an inch. Sand and when you get ready to put the clear on move the tape line up a little more and spray. This way, the under coats (primer, color) are completly sealed in with the fuel proof clear and there should be no way for the gas to come in contact with the under coats that may not be so fuel resistant.
The 1/4 inch and 1/8 inch are just estimates, but I think you'll get the general idea of what to do.