I feel with an old gutted trailer you get that much more work that needs to be done, that is you now have no patterns to go by, thus making the rebuild that much more work. If these trailers were all at 90 degree angles then that would be great, but
fiberglass trailers are all rounded angles and patterns would have to be made for everything. If you want a gutted trailer, buy a cargo trailer and get to work, I see them a camping grounds all the time.
trainman