Getting rid of saggybutt syndrome is lots easier than you might think.  At
the top of the spring in the rear of course is a black rubber spacer.  Visit
your local experienced parts emporium and get some, four would be nice.  Or
as the bent one says make up a couple from a white plastic cutting board.
Jack up one side of the van at a time and you will notice that just before
the tire lifts off the ground you can undo the 19mm bolt that retains the
shock absorber.  The swing arm will now allow the spring to almost fall out.
Place the new spacers on top of the old one and jack the suspension
sufficently to reinsert the shock mounting bolt.  Tighten to specification
and move on to the other side.  Repeat as necessary.

Enjoy the ride.

pensioner