Rivet trailing edge of step on skins

The trailing edge of the step on skins was previously left unrivetted pending a decision on what to do with the hole mismatch (due to bend tolerances). This mismatch was as much a 0.7mm in both the forward-back direction and the inboard-outboard direction. Flexing of the top step on skin could mostly reduce this, but this would lead to a slight bulge visible from the top side. So instead I left this skin relax and upsized-recentered these holes to 4mm, resulting in perfectly aligned holes for all three layers (the skin, bottom skin, and rib).

The rolled lower skin edge was fay-sealed with Sikaflax Pro+