Once I had the placement of the skin over the ribs and spar finalized, I drilled and clecoed the two end ribs to hold the skin in place. This seemed like a good idea because only at the ends could I see exactly where the flange relief divots were, and make sure of getting the rivets into the flats between the reliefs. But with hindsight it seems this was a mistake, leading to excess material in the bottom skin after the top skin was drilled and clecoed. It seems that a better procedure would have been to clamp mason's twine at the rivet locations at each end of the skins and use those twine lines to plot the inner rivet hole locations, then do the drilling and clecoing from the middle rib outward and from the leading edge backward. That's the way I'll do it on the left wing. For the right wing, I'll temporarily remove the end clecoes and work out from the center, hoping the end ribs are flexible enough to move out.
