Empennage: Rudder. Counterbalance rib riveted to spar.

I decided to redo my rudder due to the trailing edge.  Here is the post outlining the new rudder.

I wouldn't normally post for such a mundane task, however I wanted to document my approach here.

Squeezing rivets sometimes causes thin parts to distort, especially rib flanges.  Since this rib will be holding up a hefty bit of mass, best to keep the flange as flush against the spar as possible.  So for the rudder counterbalance rib, I wanted to buck the two AN470AD4-4 rivets with their manufactured heads on the forward side. 

Bucking the rivets would require an offset rivet set.  With the requisite higher air pressure and spinning rivet set, I wanted two hands on the gun.  So I propped the bottom side of the rudder spar up with wood blocks.  The top side of the spar, with the shop head(s) protruding, was rested against my dumbbell bucking bar with a steel plate under it (the latter mitigates the dampening of the gun blows by the wood).  In no time, I had two great shop heads and a nice flush rib flange.