The following instructions are from www.solsticeforum.com
If you are like me (lower back problems from time to time) , I
wanted additional support in the lumbar area of our seats. I found a very
inexpensive solution that has really improved the riding comfort. An
adjustable inflatable lumbar air bag can easily be installed in the seat back
by anyone capable of minor dyi skills. This unit can be purchased at Universal
Inflatable In Seat Lumbar Air Bladder.
Unzip both sides of the seat back and lift up the cover which
will expose the support frame and the seat foam.
Use a light coat of contact spray adhesive on both the backing plate and air bag, allow to "tack up" and position the air bag on the plate.
Zip up the zippers and feed the squeeze bulb between the seat
back and seat bottom. I wanted the bulb on the inside, but it's your choice.
It has really made the seat more comfortable on long trips.