As always, the "ergonomics" of the pit is hard to nail down right the first time, that is why some people start off with a cardboard mock up. I did my pit in Sketchup, but even then I had to do some adjustments especially on the screen-height part.
And remember --- if you at any point change that chair...
That was one of the things I wish I would have seen before I started mine. It didn't even occur to me to mock it up with cardboard
I was browsing the forums here and saw someone show their mockup and I was like "GENIUS"
I tried playing with sketchup but was not having much luck getting it to work. I just can't think in 3 dimensions when dealing with computer models for some reason.