Very tedious, but got the aileron parts all prepped and primed. Got all of the stiffeners, ribs and skins dimpled and prepared for assembly. Back-rivetted the top right skin and went to start on the right bottom skin; realized I had two bottom left skins. I had taken my time to correctly identify and make separate top and bottom skins for each but I guess I messed up. Ended up priming and dimpling two left bottom skins. Not worth trying to correct. Ordered a new bottom skin from Van's. 8/15: back-riveted the left top skin. Purchases: Van's- new bottom aileron skin