Lumbar support ideas?

All -

For the third year in a row I've somehow managed to injure my back
early in the season (base of the spine/sciatic nerve). I'm beginning
to suspect its not my day-job or rigging my ship (I have a one-man
rigger); but rather my flying and seating position in the cockpit
(DG-300). Short early-season flights don't seem to cause a problem;
but a couple of long flights in a row (or a long drive in the car + a
long flight the same day) may be what's touching it off... Its
getting VERY frustrating to be bed-ridden for a couple of days (at age
33)!

So while I get going with physical therapy (again) and meds (again),
I'm thinking about ways to change my cockpit and take pressure off the
base of my spine. I've already added some seat-foam; the only other
thing I can think of is to try not to have my spine bent in such a "U"
shape.

Anyone out there have suggestions on creating a lumbar support pad?
As I understand it, the pad should sit between the parachute and my
back (not between the 'chute and the seatback). Tips or ideas would
be greatly appreciated!

--Noel