So after first connecting the engine the other way around, rain , and more rain, I finally managed to make my first flight in Stabilize mode. With just P-control on a Wingo clone, both at 0.06, it manages to maintain it's height perfectly, but it rolls around a bit.
Guess upping the P was a bit enthusiastic! I'm not posting anything revolutionary, but I'm very happy it flies :)
Picture of the APM mounted inside the plane, no video, sorry.