[duke]

Just finished the seats using the B&B shells and they feel pretty good. Per previous posts the key is the foam! For the back I used 1/4" closed cell high density foam for the base layer. This is the foam they used for vinyl tops. Even though it is only 1/4" it will not bottom. Followed that with 1" of high density 60# foam, and then 1/2" low density glued to the leather.

For the seat base started with the 1/4" closed cell, 1" high density were you butt fits and 2" of high density under your thighs. Topped this with 1/4" closed cell, and 1/2" low density on the leather.
The seat mounts need to be higher in front (3/4") so the seat tips backward until the bottom of your leg touchs the seat in driving position.

A few more dollars and some time but a very comfortable seat.