Thanks for the input everyone. Here's some answers to a few questions-
The big square in the middle of the CP would be for a 3" trackball. I used the dimensions from the HAPP site since I've only install the 2.25" version from Ultimarc.
I originally had a little bump out at the bottom to increase the depth by another 4", but the bottom removable panel would have been harder to mount than if it was straight. I also considred just making the whole back straight, but I like the look better this way. I think the center of gravity for the TV should be in the middle of the cabinet, so hopefully there won't be any stability/safety concerns.

This cabinet would be to sell. My brother-in-law's friend saw my UA-I and wants me to build him one. However, I wasn't very happy with the UA-I design and wanted to try my own hand at designing a cabinet that I could cut and assemble easier. We'll see how it goes....
