- Countersunk rear spar doubler. I accidentally countersunk one of the no rivet holes. My solution: I dimpled the spar so that it fits flush and should it get a flush rivet, I will use JB Weld as putty to flatten the dimple out. - Dimpled all the skins and corresponding holes in the spars and ribs - Scuffed all surfaces that will be primed with maroon 3M Scotch Brite.