I don't mean to nitpick, but as drawn the Green wall is 10' 6" and that will make a difference when you start adding track. The upper jut-out on the right is 4' 8", not 4' 6", and that may or may not make a difference, but I thought I'd point it out just in case.
And just for the sake of total clarity, I'm assuming the dimensions are inside measurements and the walls you're going to build will all go on the outside of this space. That may seem like a small thing, but I've seen people add basement walls that end up taking away from the actual interior size of the room. Normally that doesn't matter, but model railroad designs are a matter of inches, so losing 5"-6" to walls can be a big deal if not accounted for in advance.
NOTE: This is referring to the SCARM file Aegis posted, not Jan's file. Jan was posting as I was composing, so I didn't see his post. Fortunately, Jan used the file with a 10' wall and his choice of curves fit. 
