I experimented with an airfoil shape on my IFO. It is easily done with some small pieces of balsa bent to the right shape. You just shove the plastic covering into the shape you want. I "think" I can make it fly slower. The good thing is that since the mod is cheap and easy and can't hurt then might as well do it and see what happens

I also put airfoil in my Stubenflege slow flier. It looks better that the flat wing and, I think, flies slower.

If you are seeing a trend here it is that I don't really like flat wings. They just don't feel right.