I thought that it helped both inside and outside manouvers. I read this somewhere; inside by slowing response for small corrections for a smoother look. Outside needed a bit more crisp control; no matter how good the plane flies upside down it still flies better right side up, and the extra bit of control balanced out the instability. One thing I think that is important is that Prettner designed his planes for himself like a custom set of golf clubs. He must have learned what helped his problems to gain perfection.