Lynn -

I use a "Long Softie" chair pack.  The chute is spread over the length of
your back, and it comes with an attached seat cushion of roughly equal
thickness.  More comfortable to wear than a conventional backpack or seat
pack arrangement, and minimizes any changes to your seating position.

Alan Silver is a parachute guru extraordinaire.  He is very generous in
giving advice, and I highly recommend that you give him a call to discuss
your requirements: (510) 785-7070, http://www.pia.com/silver/articles.htm

Regards,
DJ Molny
Extra 300/L owner & regular parachute user (er, wearer, to be more precise)