I started riveting on the main top skins. I back riveted using the bucking bar with this large flat face and the double offset back-riveting set. I put a balloon on the bucking bar so it was too cold for my wife to handle and tape on the flush head so it wouldn't move as much. I was lucky to get some volunteers to help hold the bucking bar. And they did a great job.
UPDATE: I have two warnings for using this back riveting process. 1) use more air pressure. I used about 40 lbs and should have used 60 pounds to get the rivets to squeeze faster. 2) watch alignment of the 12 inch rivet set. Just a little mis-alignment bends over the rivet and makes them clinched shop heads. I ended up drilling out over 100 rivets and reviting them using the normal forward rivet process. I also drilled out the entire row along the main spar web. I still have many rivets slightly clinched and many with shop heads to large.
