Deburring and priming (cortec) rear spar (left wing). Also, decided to drill out rear-rib to main spar rivets, on Rear Rib #8, and put a backplate on it due to a pilot hole that's a we bit off from the actual drill hole. Primed and re-installed. The backplate is on the rear rib front flange and is the same-size as the whole flange spanning all five of the A5 rivets.