On mine they did the floor 1st, then ceiling plywood then the interior plywood. that way all the outlets can be wired and insualtion installed. On mine they stpled the insulation to the interior plywood sheeting every 2 or 3" to keep the insulation from pushing out against the alum skin causing it to bow out.
Donnie Barnes took a lot of pictures of his build. if a picture is worth a 1000 words, his pictures are worth millions!
Transport designs built Donnie's truck;
Donnie Barnes Coach build
good luck, we need more pictures of your build too!
-blizz