For those that don't know Steel and Aluminum don't like each other. They can have a galvanic reaction, so to avoid the metallurgic reaction airstreams were designed kind of like a sandwich. The steel frame below, the plywood floor that covers the entire frame and the aluminium shell that fits to the plywood floor pretty snuggly...
Right on top of the plywood there is a C channel that runs the perimeter of your trailer, it is called a C but it sits on your floor like a U.
The side of the U facing the exterior wall is buck riveted to your exterior shell, those rivets are within your lower belt line. To do this kind of shell on flooring job you do not need to do anything with them, leave them be.
You will just remove the stuff that faces the bottom of the U and of course the inside wall of the U is where the lowest row of your interior walls rivets are placed. Once the interior walls have been removed and you have exposed your C channel you will see that you have a bunch of philips screws to easily remove but there are bolts coming upwards and all of them bent... Those are the elevator bolts. The factory bends all of the bolts so that the nuts on them cannot wiggle themselves of with the vibration of travel. You will find that your elevator bolts are installed pointing downwards in the plywood floor area. So it means at this point you will need to drop the portion of belly pan to be able to access those. It a good time to get your trailer to a nice level area because you'll be here for a bit.