It is thunder and lightning-ing out, so I'm taking the time to catch up on the build log.
Two weeks ago I insulated the wall cavities and put the original plywood back on.
Now, as any decent mechanical engineer will be able to tell you, those metal studs conduct a lot of heat through the walls. I put my hand on the horizontal metal ribs in the nose of the trailer when the sun was shining directly on it, and it was so hot I couldn't hold my hand there for longer than five seconds.
This means that cavity insulation by itself does precious little to actually insulate a metal-framed structure. Letting heat in is bad enough: the real terror is the condensation issues you can get inside your wall assembly when it's cold out (think mold, rot, rust, etc).
Long story short, the walls are only half done. I'm adding another layer of continuous insulation to the inner walls.
The somewhat odd placement of the panel is to reduce visible seams - the bottom seam will be covered by a bench, and the left-most seam will be covered by a shelf.
Most trailer builders would probably recommend furring strips to affix the panel to the wall, to make the surface very smooth. This is good advice, but those furring strips are just heat fins to me, so I'm giving this route a try. The panel/insulation sandwich is screwed into the 1/2" original plywood with decking screws every 6" on 16" center, it feels very firm, and the surface is actually rather consistently flat.
The rest of the wall insulation should go up quickly, and then it's on to other exciting things.