The only way I can think of is to start by using a power tool that can make plunge cuts between the luan that’s on the back of the filon and the camper framing. The tool I’m thinking of is a Rockwell Sonicrafter or any of the other brand oscillating blade multi+tools. You’re going to find that there are staples around the edges and compartment doors. The right oscillating blades can cut through those staples. The longest blades for those are only about 3” long though.
Once you’ve started separating the skin from the framing, you may be able to use something like a heavy duty floor scraper to finish the job with brute force. The type of scraper I’m thinking of is the type used for old flooring demolition to remove ceramic or vinyl tile. They have a long handle, and heavy forged steel head that can be sharpened.
If you go the brute force route, find some young stout guys to do the majority of the work for you. That kind of work is hard on older guys joints.
:):)
