Started attaching the bottom skin on one flap

After verifying that I had no twist, I removed the protecting sheet

I tried to find a way to use the special elevator bucking bar but could not make it work

The first rivet in the bottom skin, I can not imagine doing this without a tungsten bar

doing every 10th rivet as mentioned in the plan to prevent twisting

marking the ones done

after doing every secind, I did the last 50% bay by bay from the center and out

finishing with the spar rivets

And using the squeezer for the outmost two 

"only" pop-rivets and the trailing edge to do on this flap