Unable to stand the pain anymore, my wife bought the Corbin Gunfighter
and Lady with Passenger Backrest for my Hawk GT.

It came with no instructions, but it came 2 weeks earlier than they
said it would.  Installation would have been very easy, but the seat
fastening hardware was apparently always on the wrong sides with
the stock seat!  It never was easy to put on.  Once I figured that
out, the new seat went on the first try.  The passenger backrest, though,
does not fit as I thought it might.  The supplied screw to set the 
backrest angle does not fit, and I have not yet found a suitable, 
hard, ( SAE grade 8, or perhaps 5 ) 1/4-20 bolt that fits.  There is a
a soft bolt in there now -- just don't lean back.

The driver's section of the seat is a bit wider.  Seems comfortable
enough, but then again I put about 5000 miles on the stock seat
without a thought.  The passenger's section has about 8 times the 
volume of foam that the stock seat has, and from my short test it
seems much more comfortable.  The backrest helps a bit, but I've not 
has enough time to really test it.  The backrest also comes with a 
small pocket.  Its now more difficult to swing my leg up over the 
10" taller seat.

If I go on the three-notch ride soon ( Dixville, Pinkham & Smugglers),
I'll give a more complete report, but in general it seems like an
improvement.