SS40 is one of the nicest planes when it's slow I could imagine. You really have to be crawling along for it to stall. I noticed you said you used rudder, did you mean alieron? My first reaction would be that the alieron servo is backwards. BUT. If you were using rudder, it's possible on some planes to give a little too much rudder, and the plane will roll back the other way. Dosen't sound like it rolled opposite, so it's just a theory. What was the weather like? Our field gets burbles that will drop a plane 20 feet in a hearbeat, usually right on final.

Andy