Ok...going to sound crazy......this past weekend at a local race I noticed a guy had a airline that extended out past the base of the seat. I asked him what it was for? He responded that he has back issues and can't stand riding, so he sits down most of the time...sure enough, I watched his moto and he was sitting except for the jumps.....
He went on to explain how he made an air seat............. They way he explained it.
1. Cut out the foam.
2. Inserted a tube - didn't ask how big or what type? I should have asked!
3. Inserted a tube into the cavity.
4. Trimmed foam away that once filled cavity.
5. Made the foam fit over the tube so it looked OEM
6. Put on the seat cover
7. Ran a nice air line from the valve stem of the tube beyond the seat base / rear fender area.
8. Secured the airline with the valve stem cap down with a small zip tie.
9. Uses a small bicycle air pump to adjust the PSI of the tube, or a valve stem remover to let air out.
I wish I had taken a picture of it.....freaking trick...looked very normal.....but he stated that it works excellent and has not had any issues.
The seat looked perfect, no weird bumps, humps or anything crazy.....just had a nice cushy but yet firm feel to it when I was pressing down on the seat.
I'm sure there is trial and error to be had, but it was trick and meet his needs.