Steve: Here are some more pics of the inside of the stand. You'll see how pretty bulky it is up underneath the stand. I believe it should hold up even without the center brace. The walls of the stand are 3/4" thick, so along with the 2x4 it is pretty strong (I think!?).
The removable brace is about 1/32" smaller, it sorta just slides in. I milled out a delrin bracket that it will slide into, and I was thinking of using some removable dowels that just hold it into place. Its more of a security thing I guess. I'll post pictures of that once I install it.
(click on pics for bigger pictures)