In the first picture, both the left and right top skin have been riveted on. The top center section skin is about to be riveted. I put the assembly on its side for easier access to the front and rear rivets.  I riveted the entire aft fuselage section by myself. I was able to do that with a combination of good positioning to be able to hold the gun and bucking bar and doing everything that I could with back riveting.

Back riveting is a great technique, but it does take careful positioning of the piece to make sure it is supported to keep the section to be riveted flat on the back riveting plate. I started at the front by bucking the rivets as far as I could reach comfortably and then switched to back riveting the middle section, including the two middle bulkheads.

Picture three shows the assembly turned on its back as I back riveted the top rivets.  Then I turned the fuselage on its side again and reached in from the back to get the rear most rivets by bucking them. The aft fuselage is mostly done in the last image.