The Pfalz DIIIa stab was flat on top and airfoil shaped on the bottom. The engines really do not care what position they're in, I run several of my engines inverted. On our 1/3 scale Pfalz kit the 85cc is straight up and the top 1/3 of the dummy engine is still used, the side cowling plates conceal the engine. We will be doing a 1/4 scale soon.