hey raindav the concave on the control surfaces is a nice touch however I will seal off the ailerons and elevator halvesany way from the bottom surfaces using adhesive mylar or simlar, as I think it is really an important process not to be over looked with any aerobatic aircraft- that I have attempted to fly; as to my control surfaces I would of preferred @ this stage, to have used the more conventional approach to hinging------- but following through to see if the performance improves over traditional tapered control surface leading edges. One thing for sure with BLOW BACK todays G.S. servos offer the answer just look @ the speed and Extreme high torque of the new and current Jr8611As, I think it is noticeable[8D]