The aux tank outlet hole conflicted with the stiffener between the 1st and 2nd lightening holes aft of the spar. I removed the rib and made a new one with a curve using a stretcher so as to get it away from the outlet hole. Everything went fine until I went to manually rivet the last rivet. Unfortunately, the rivet set I used was too short, caught the edge of a panel cutout, and bounced off the rivet. By the time I got my finger off the trigger, three punches had been made in the rib, cracking it. After a few choice words, I stop-drilled the cracks, and constructed a .032 2024-T3 doubler to reinforce the damage.