If I were contemplating this re-modeling job, I would seek out an RV repair shop and buy one/some of the guys a few cups of coffee (adult beverage) and have a discussion about how trailers are constructed. I've never heard of fasteners through outside walls.
Sorry I can't be more help.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"