RE: I need a fuelproof clearcoat... Help...
If you have (or can borrow spray gear) look at Nelson's clear WITH THE CROSS LINKER. It is supposed to be good to 25% nitro (definitely good to 15% nitro). I have heard of people getting good results with Nelson's using a foam brush - I haven't tried it using a foam brush.
You might also want to look in an auto supply store for a rattle can of clear ACRYLIC ENGINE ENAMEL (I have only seen it in gloss). I have used this successfully over latex with 15% nitro. If you decide to go this route, make sure the paint on the covering is COMPLETELY dried/cured before putting the clear on, and let the clear dry for a minimum of 5 days before exposing it to glow fuel.
Waterbase polyurethane is fuel RESISTANT with the following caveats (waterbase poly will not yellow, however, the oil base poly will yellow in about 6 months):
1. Let the poly dry/cure for A MINIMUM OF 7 DAYS before exposing it to glow fuel.
2. In areas where the exhaust will be hitting the clearcoat use 2 or 3 coats of the waterbase poly.
3. Do not let the glow residue remain on the plane/finish for over 4 hours - at about 4 hours the finish WILL soften.
I have several planes done this way and have had no problems as long as I followed the caveats above (this was before I found out about Nelson's paint & clearcoat).
Hope this is of some help.