For a quick test put a partially inflated paddle float under your thighs. adjust the amount of air I found this helped me alot, nearly curing the problem, easier to do than a custom seat and more adjustable.

I do, of course make my seats with support under the thighs which seems good for most people. The back rest should also be right...also not an easy or trivial problem.

: Toni,

: To help out until you get a new seat, try moving the thermarest forward a
: little to give more support under your thighs. It works best for me if I
: can just feel the back edge of the seat when I am sitting on it. You also
: don't want too much air in it, let air out until you feel more support
: from the whole pad. This is just a temporary fix until you can get a much
: more comfy seat installed.

: Mike