Automotive Clear is fuelproof(not the cheapstuff from spray cans) and can be flattened by the addition of a flattening agent that you can buy at any automotive paint supply store. Automotive clearcoats are the only ones, in my experience, that do not yellow with exposure to UV rays from the sun.

A friend and I just finished clearcoating my Jet Model Products T-33 this weekend. It required a flat finish. I used Dupont Nason Clearcoat, thinned 100% with medium reducer and added 50%(by volume) flattener to it. It will never yellow no matter how long it is exposed to sunlight. All of the jet guys use automotive clearcoats.

Chevron Perfect clear is fuelproof but yellows pretty badly.