The thigh bolsters on the lower seat cushion of my Van are
permanently crushed from age.  I'd like to replace the cushion
foam, but can't figure out how to remove the upholstery.  There are
four small bolts that hold the seat rails to the metal seat bottom,
but how does one remove the large metal plate, that appears to
cover the edges of the upholstery?  Thanks in advance!

Cary