Teardrops n Tiny Travel Trailers

There you go. You just can't beat the voice of experience.

I did like the first pic tony.latham shows. 1x2 layed flat, 3/4" foam in the voids, 1/4" plywood exterior, and 5mm luan interior. If I do it again, it'll be 1/8" interior, 1/4" exterior. It ends up being amazingly strong. As long as you glue all components on all sides. It creates a torque box.

Anjib is right about stick framing. Here’s how a 60 year old camper was framed, and except for water intrusion, would have lasted another 60 – notice the butt joints and lack of continuity?

However, my motto seems to be “why just do it, when you can over-do it?”
I put them together with lap joints, glue, screws, biscuits, kregs and any other un-necessary attachment method possible.
Anything that you build will probably be strong enough; your biggest enemy will be water (and people on cell phones).

I guess I can't help from looking at this differently. Had the wall frames been originally built as sturdy as your reconstruction, the assembly may have been more stable resulting in less relative motion and less degradation of the waterproofing treatment that may have been in place. Now if it was poorly waterproofed to begin with it may not have made a difference, but I would rather have sound waterproofing over sound structure (yet still lightly built) than neither. Just saying.