I've been playing with paints too in anticipation of a cowl repaint on a Hanger 9 PT-19 and cowl and wheel pants on an Akrobat. Test so far are

* Rustoleum Professional high performance enamel... 24 hours later it softens immediately when a drop of cold fuel is placed on it. However, if given a couple of weeks cure time, the Rustoleum paints seem pretty resistant. The Rustoleum clear coat enamel however is not very resistant.

* Dupli Color from the auto parts store... cold fuel doesn't soften it... even within a half hour, however.... when I clear coated over the Dupli Color with some Dupli Color truck, van and SUV clear coat... after 24 hours, and tested two hours later... the fuel softened the clear coat and the Dupli Color color paint under it that previously had been totally resistant to softening with cold fuel. So... as has been mentioned... strange things happen with paints.

* The Dupli Color Truck, Van and SUV clear coat over the 24 hour old Rustoleum enamel produced instant crinkle finish.

* I'll test again after a week or so the clear coat over the Dupli Color color sample to see if it still softens.

* I've also tested one of the Dupli Color acrylic paints and they are not affected by cold fuel. Not many color offerings of the acrylic locally but one is very close to royal blue ultra coat. I will use it to repaint the PT-19 cowl.