Hi, I HAD the same problem with drilling the holes. What I do now to much success, is to first line up the control horn, and use a sharp pencil and poke a hole, then use the correct drill bit size and carefully drill STRAIGHT. A right angle cordless drill makes this easier. You can also make a little jig by getting a piece of aluminum or hardwood, aluminum is better, about 1" thick or more. Drill the hole (using a drill press to insure a straight hole). The guide doesn't need to be big, 2" diameter. Then use that as a guide. WHEN YOU DRILL THE HOLE, do it at low speed, NOT IN A HURRY, concentrate on looking at the angle your drilling. With the jig I mentioned above, poke the bit through it and rest it on the hole the pencil made and keep it flat to "plane" you want. Ailerons are usually tapered, so make sure it is flat to the plane you want and NOT flat on the aileron.

Hope I helped,
Joe