I had forgotten about the prototype seat story. Tom also said they were going to try a higher density of foam that was molded with shape but was overruled.
The spacer issue is another solution I used on all of the AmeriSport GT5-S cars because the pans were dropped flat and is you did not space the front of the seats, it felt like you were slipping forward--HORRIBLE!
Removing the rear spacers and adding them to the fronts will help allot---the later car spacers were welded in---earlier one were aluminum blocks. If you have an later car with the longer seat tracks, you could replace them with the shorter tracks and move the front mounting holes in the shorter tracks to the longer track forward mounting position. Then re-drill the rear mount holes without any spacers spacer which would also drop the back of the seat. The bottom of the seat when all the way back will be touching the floor using this approach and will give you the max head space height without cutting the car.