Air can slip from the lower to the upper suface of the wing through these holes where the ailerons attach to the plane, adding drag.

To combat this, RDD (my build-shop) added some carbon-fiber leading edges to the airlerons... and then a TON of body-filler behind that leading edge ... for some reason.

The aileron on your LEFT is how it looked when RDD thought it was 'done'... the white is body filler. The one on your RIGHT is one of the ailerons once I was done with it... the black is carbon fiber.

I got nice and sweaty doing all that sanding, but as a result of that workout, I weigh a few ounces less, and the airplane weighs several ounces less as well.

Also, the light aileron, with less weight aft of the control hinge, will be less likely to flutter. The aileron at right is how ailerons should be! Of course, I made the one on the left just like the one on the right after this pic was taken.

Here I am doing the final, careful, hand-sanding of the aileron, with the rudder sitting there as well, also brought down to a bare minimum of body-work.