Yes fire box is insulated 2" (Super Efficient) . You are right. The upper rack are in the way of mine. I have shorten them by 6" from the pictures in the tread
. Plus they are removable. If I had it to do over. No upper racks, but I would have a sausage bar to hang and smoke sausages. On mine, you have to the bottom racks out they don't slide. I think that might bother some but works for me. Paint I was going to paint mine metallic grey from http://www.kbs-coatings.com/
, but things changed. And the Mrs. liked black so that is the way I went. I'm only about 90 miles from you I might come check out your rig someday when you finish.