The aileron construction is a little fiddly. You have to attach ribs to the pipe, which I’ve found alignment to be a pain. Drilling and countersinking the pipe leading edge is also a bit of a pain. If these holes aren’t plumb(?) the rivets will pull crooked and ruin the finish of the leading edge.

Dimpling the aileron spar, like other tapered spars, is a little tricky to ensure the squeezer doesn’t create small distortions in the flange angle.