I tied a string to the middle outside of the skin, looped it through an eye bolt I have in the ceiling and tied it off. As you can see in the second picture, I used a sardine can in reverse technique. I riveted the skin to a rib, then the skin to one bay length to the front spar and then one bay length to the rear spar. Then I would let the "lid" down to close the next bay. The worked pretty good except that it was torture on my arms. I had to put my arm the the second to last lightening hole and then bend my wrist 90 degrees to hold the bucking bar under the rear spar. The fourth picture shows the marks that were on my arms 30 minutes after I had finished.
Then I riveted on the the hinge for the flap.
I am glad that is over with. The right wind is "done". I reattached the tank, flap and aileron. I did this partly because I flet this was the bets way to protect them, to keep from loosing or using the parts elsewhere but mainly because it looks cool.