Only two-part epoxy paint is actually FUEL PROOF. Everything else is FUEL RESISTANT to some degree. Lusterkote, according to the Tower website, will not be damaged by raw fuel up to 15% nitro.

You are right though, waterbased Poly will get gummy if exposed directly to the hot exhaust. Using it on floats or seaplane hulls should not be a problem, particularly if you wipe off any raw fuel spills right away.

Jim