I just been looking at pictures from the Simpit site on SimHQ and linking to some others. I think each pit is sort of personal to the guy using it. I had to combine the features of a flight pit with something I could use for racing too.
I've just been winging it after thinking about it for about 6 months. Got the seat first. It sat here for almost 6 months. Then one day in about two hours, built the back. That sat here for about 2 months.
Then thought about it alot more and decided on the two monitor placement. About the same time I wanted a large screen but the cost of a 21" monitor is just too much for the average Joe. So I bought a Fresnel lens ($56.00);

http://www.simcockpitsystem.com/Detail.bok?no=18

and that led me to about the dimensions I have now. I built the front half in about two hours after ecieving the lens. I have no plans, just building as I go along. Tape measure, ruler, saw, just start cutting. I use the "if this is here, this HAS to go here" type of building method.
Funny, I took measurements just the other day for eyesight to lens distance and floor to height distance based on a mock-up. I went out to cut it from the plywood and changed all the dimensions right on the spot. Wasnt even close to what I spent days on mocking up. The goal was to stay within the one sheet of ply for the front monitor half.