Good points to think about Fugtive.
Again thanks so very much for your help.

No problem. Two more things I though of, not about seats but important none the less.
Do a lot of mock up. I had an old stick I kept out in the work shop as I built mine. It was in and out of that thing a hundred times. Getting things lined up well is as important as a comfy seat. If your stick position is too high by a half an inch you'll be cursing yourself.
Placement of your computer box. Mine was across the front sticking out a bit to one side. Upgrades on the computer where a nightmare as I had to move the whole simpit (seeing the front was against the wall) to get the room to disconnect the wires to pull it out. After a few upgrades I though that I should have made the tower sit on a hinged platform so I could flip it out to expose the side cover that I needed to remove to install parts. That way I could work on it while it was still connected/in the simpit.
If I think of any other mistakes I made I'll post them for you. Keep us posted on your progress, I'm interested to see what you come up with!
Good Luck!