I am also looking at ground mount 10kw system but bifacial set up as a fence running north south but having design issues the way our electrical is set up with backup generator
When we did our ceiling 4 yrs ago they put up drywall and no vapor barrier and 3.5'' of foam so far so good. If we were to do again i think I would vapor barrier it.
I would wait after Nov of this year there is a new code book coming out, going this week for the 2 day coarse on it and will see what the changes will be. With that been said if you put one in this yr and get it inspected but i would wait till you have your building staked out.
When I reported it they ran plates and trailer and nothing come up. Strange thing is why steal it then dump it there. They said they would update me, for sure contact owner and get there side of story.
This trailer sitting at Shinning bank lake day use area for at least 4 days called it in to RC's and not reported stolen as of this mourning. 2 bikes not tied down and looked like bouncing around.