My passenger seat (out of a duece) I redid with 4" upholstry foam in place of the springs and horsehair pads. I like that seat sooooo much better than the springy stock driver's seat. But I can't drive from the right seat so I'm stuck bouncing along.
Nice thread, fishtail. Did you re-tack the back panel to the top of the seat frame? Looks like someone did. I had to on mine. I also added a strip of 1" wide 1/8 thick strap for reinforcement.