I know of two seat-backs that are available:

First on the scene was the sling-back.  This is basically a plank of plastic
for the spine, supported by a pair of straps that connect to the side-rails.
It's crude but effective.  I've never missed it while buggying, but it's damned
comfortable for when you are sitting around afterwards...

Dean Jordan was showing off a complete replacement seat at El Mirage.  This
is suspended all the way round by bungee chord and is all padded, so it is
very comfortable.  It smooths out the bumps of the ride (useful at Berkeley...)
and doesn't dig in to my back like the Lynn seat does.

Andrew


There is a seat back for the buggies like you describe.. It is originally
the design of Julian Wolfe-Patrick, and is being produced by Moran
Precision Aerobatics.. The Springback is a great addidtion to your buggy,
and will fit both the Lynn and the Cobra buggies.. It's nice to have some
back support while sailing a long reach.. You should be able to get the
product soon from your nearby buggy dealer, or from Windborne Kites,
Monterey, CA, or from me.. Moran is only about 25 miles up the road from
me, and I've asked him for a new product release and will be posting one
shortly..
Dan Rubesh