The foam places around here sell junk. On the last seat I did, I went to a sports equipment place and got an excersize mat (about 1/2" thick), cut my stock seat foam in half longitudinally like cutting French bread to make garlic bread (using an electric bread knife actually), and put a piece of exercise foam in the middle. Gave more support but still had cushion. The seat before that, I went to an auto uhpolstery shop and just bought a big wad of good firm foam.