I had the skins on & off twice today in order to adjust the rib flanges. The rib is stronger than the skin so if the two are not in contact when riveting, the skin will bend down to the rib leaving a dent that is a bit unsightly. I think I have the ribs to a satisfactory level so I have primed all that requires priming & tomorrow I'll cleco the skins in place again, I hope then to be able to rivet them on.