Some things on the horizon:
-The trim profile I got from phoenix is 1.25" tall in the top section and my roof perimeter framing is 1" square tube. I am thinking of adding 1/4" of XPS foam to the underside of the roof (between the frame and headliner) to ensure the top of the trim is below the roof perimeter. The stack of materials with the roofing, wrapping the sideliner, etc. would probably be ~1.2", its likely better to have to top of the trim a bit lower I am thinking.
-If I add the 1/4" insualation noted above I'll likely skip the roof electrical boxes, I can just make a pocket in that zone under the slat areas for the wiring connections. I think I am going to screw down the slats rather than staple them so I can get the tension right while compressing against the 1/4" XPS (versus just being against the aluminum tubing), with that in mind I can back off some screws when needed to access the wiring.
-In the roof I am leaning towards using polyiso rigid insulation with the foil face towards the camper and then totally taping off all joints with aluminum tape so it will be a vapor barrier. The 1/4" XPS is perforated and so is the marine headliner so I would assume any condensation against that vapor barrier should have the ability to work its way back out either in liquid or vapor state. (Anyone more familiar?).
-Roof, I am likely going to go with a 2 piece corrugated roof (stiffness and some flexibility of the sheeting), I haven't decided on 2" raised/2" valley or 1" raised and 3" valley yet. I will screw it down with roofing screws and sealant.
-On the roofing framing ATC puts down what appears to be foam strips similar (if not the same) as truck cap foam tape which is 3/16" ($7ish for 30'). An alternative option I could use is off brand double sided foam tape that is .08" thick ($12 for 50') to add a bit of extra grip. If the bond fails its not a concern since its still screwed down. I'm not sure if this would cause and unintended issues, can anyone think of anything?
-Siding, I am thinking of going with a more subtle brake line reverse pattern like BBZ did with his siding on his project rather than the more aggressive mesa pattern with more taller protrusions.