The biggest obstacle was the lower door hinge attachment. Very strange rivets, heads shaped like Maddonna's bra, but it turned out they were 5/32" solid rivets that were easy to drill out. You can see the aluminum backing plate in the left photo. This plate was very tenuously held onto the ribs, but was mostly in place due to the rivets through the outer skin.
Here's the steps we went through:
1. Remove inside closets, partions, and partion rails.
2. Remove fiberboard wheel well covers.
3. Remove door hinge pins and remove door.
4. Drill out lower hinge rivets.
5. Drill out all inside skin and outside skin rivets.
6. Remove lower outer skin.
7. Remove lower inside skin.
8. Use outside skin as template to match drill and shape new skin. Don't match drill all holes on the bench--consider using the joints where other skins are on top to match drill with the new skin in place on the trailer. Cut the new skin to provide a very slight overlap of skin to the door frame.
9. Reinstall the hinge backing plate using flush solid rivets.
10. Once all the holes are checked across the entire skin (in place), apply Vulkem to appropriate surfaces and put the skin in permanently. Continually monitor the placement of the ribs and the alignment of the inside skin holes to the ribs. Pay close attention to gaps and joints along the wheel well and the "C" channel immediately adjacent. It may require significant gasket, eg, maybe some butyl tape and certainly a liberal application of Vulkem.
11. File the skin down to match the door frame (there was a very slight curve in the door frame, about 1/16" over the height of the lower skin, that made the skin proud of the frame (this is the desired condition, as it can be fixed with a little filing).
12. Replace the insulation.
13. Pop rivet the inside skin to the ribs.
14. Done. About 7 hours for steps 9-13. About 6 hours for steps 3-8.
A note here about the stringer. It was a very flimsy "C" channel of 0.032. You can see in the photos the significant deformation of the flanges and especially the web. It was a real shock to find that the inside flange of the stringer was not attached in any way to the inside skin. This was also true for a similar stringer about 18" lower in the same wall. The outside flange was only attached with 5 or so solid rivets, very flimsy indeed. Also, the inner skin joint line was about 3/4" above the outer skin line.
The stringer was replaced with a "Z" channel made up from two 0.040 stringers that had been previously fabricated by AEROWOOD. These were for larger 70s Airstreams so they were 1-34" wide and the Bambi needed 1-1/2" width. Two of these larger stringers were cut down, one flange off of each one, then riveted together with a double web to make a new "Z" channel. The "Z" provided sufficient offset so that the outer and inner horizontal skin joints each fell on a flange, so the inner skin is now firmly attached to the stringer. The shell is now significantly stronger along the skin joint and very flat.