Im giving my opinion as an owner of various brands and what I have experienced , not as a construction guru, which I'm not.
In general, I would distribute construction weight (trailer payload) on more insulation opposed to heavier filon siding. I would also beef up the 4 corners to reduce flexing. Doing this project yourself with your experience, IMO , you are going to build this a lot stronger than OEM specs (and that's a good thing, just pay attention to tire and axle load ratings)
Once you have stripped it down, inspect the frame closely. Pushing 30 yrs. on a trailer frame would be a good time to weld up the weak points from road salt and road stress. Pay attention to where the A-frame meets the front cross members. That area of a frame has been known to stress. Reinforce straps that hold exposed tanks in place.
At that time, I would insulate the entire bottom with spray on professional foam or my 2nd choice would be closed cell foam board. I would make the trailer as winter proof as possible to extend your season, offer better resale and at the same time, reduce outside noise. (you'll appreciate it when trying to sleep)
Run all water lines inside the unit and away from exterior walls/floors. Use rubber pads on the water pump to reduce annoying vibration. I would add grates in the cabinets to improve warm air flow . Adding a small computer fan on a thermostat to circulate air under the cabinets would be a plus.
Insulate with extra insulation to any (if any) exterior lines that exit the holding tank into the trailer.
An interior fresh water tank would be a better option. Interior furnace heat would keep it from freezing.
For lighter weight reasons I would stay with aluminum skin. Its easy to repair and install as you will find out.
If you glue and pinch roll filon, then you will have to un-glue and strip it to make a future repair, plus there is a lot of weight to filon and glue.
If you experience a water leak in the future the glue will delaminate causing filon to peel away. You might have to do a section repair and add a seam opposed to removing an entire side and replacing it . You might spoil the appearance if you have to do that.
I believe the MFG.'s skin it then router out the windows.
Good luck with your project , I hope all goes well .
Bob
You tube has a Jayco factory build video as well as Northwoods ,NASH trailers . Its worth a look , IMO.
