You wrote in part:
     
           My idea was to buy that foam carpet padding stuff (looks like 
           chopped bits of foam glued together) hopefully in about a 1 inch 
           thickness.
     
     I think I'd take a hint from what the stuff is intended for.  It's 
     (probably) intended to make carpet bouncy (cushion the head blow in 
     case of a roll-over?) and to insulate it somewhat from heat transfer 
     through the floor (some usefullness here).
     
     Course, how ya' gonna keep it up?  Glue will hold it initially, but 
     I'll wager that a few hot days will have it drooping.  Course if 
     you're doing a panel headliner rather than a fabric one, this is of 
     little consequence.
     
     Since your interior already burned once, I'm surprised that you'd 
     consider installing something potetentially volatile (which probably 
     will give of severely noxious fumes when burning) as insulation.  But 
     then, perhaps lightning doesn't strike twice. . . .
     
     At last look, the boys at Westfalia were still using fiberglas 
     batting.  Good enough for me.
     
     -Blaine
     '91 Silver Westfalia "Super Chief"