It occurs to me that this undercambered wing design combined with the light wing loading common on parkflyers may be the reason that a lot of the glo pilots find them hard to fly. I don't recall seeing any glow planes with this kind of wing. That is probably because those planes typically fly much faster than the parkflyers and slow flyers common to the electric community.

I recall reading somewhere that the Aerobird, flat out with a 7 cell battery is probably doing about 25 MPH and is stable probably down to about 6-7 mph. A typical .40 glo trainer is probably closer to 40+ MPH and would probably stall at 10 MPH. These speeds are all guesses. I have not documentation to back these numbers.

Glo trainers tend to be flat bottom wings and the more advanced planes have more curved bottoms. Both are more appropriate to advanced acrobatics as compared to the undercambered wing.

To them, this hi lift design may present strange behavior making it hard for them to control the plane. Of course those of us who learned to fly on this kind of plane expect this behavior, so to us it is normal.