Sancho is right... the skins export from the editor in a vertically-mirrored manner. Flip it vertically before working on it.
I tried this really quick and crappy freehand test to see if it would work.... boy, this is going to be fun
BTW, has anyone found where the P-51D, P-38, C47, B-17, etc.. skins are? (Never mind... see Pokie's answer in the other thread)