Okay, I did a bit of searching.
Here's the thread I was thinking of:
Also, there is some talk in this thread, starting after about post #10 or so:
At one time, Tom (was involved with building Trilliums) posted this image to show the construction. The outside of the trailer is to the right and the inside to the left.
The trick is that when they built the trailer, they riveted to the plates first, then attached the two halves of the trailer together with fiberglass
tape on the inside. Now, it one is to re-rivet, it's a bit trickier to keep from going through on the inside (however, if you don't mind pulling back a bit of the Ensolite, it's not difficult to re-fiberglass tape using epoxy resin. It's just a bit fiddly, messy, and time-consuming - but not hard.