I tried a different material to calm the clatter in my bus since I thought
the sheets where too expensive.  The stuff is called Coolseal and cost
something like $6-7 for a can.  It is a glass fiber filled asphalt
immulsion that is actually pretty odorless and dries to a simi-hard tough
coating.  I put this stuff on the sheet metal on the front doors, sliding
door, back hatch and the large piece of sheet metal on the drivers side
behind the front seat.  Boy what a difference, I would say atleast 2-3 db
of sound killed and the sliding door goes thunk instead of thewanggggg when
shut.  The front doors are still somewhat loud, but you can't put much
sound deadening material in there due to the windows.  Put some plastic
rapped fiberglass insulation in the sliding door and that large panel on
the drivers side which seemed to kill a little bit more sound and helped
keep the van warm in the winter.

Dave K.