Continued to rivet the firewall stiffeners, then moved on to the corner brackets. These were more difficult to set and I had a few bad rivets that had to be removed and redone. Lower corners needed extra support to keep from moving while riveting, so I used cans full of cleco's and 2x4 blocking for support. Got the lower corners done with this technique. Couldn't reach all the rivets on the F-601J angles, so I moved the firewall to the bench and used the gun and squeezer to finish it off.