I think that it is not acctually the way that the model is flying, but the Aerodynamics of the wing. The bottom of the wing probably effects the air in a way that will make more drag on the Aileron. So whenever its upside down, the bottom of the wing, (now facing up), will still have the same aerodynamic effect on the aileron than it had when proper way up. But, how does it work on a symetrical wing, where the air should be effected the same top and bottom?
I have to say so, that I am not a genious on the subject, so I could be wrong.
Robert.