Yeah, I was thinking about the whole x deal, but I had to leave for work and couldn't fix it.Looks good, but the one thing I'd change is the X in the brace. Doing a + that reinforces the longer spans of the brace is much more effective since the brace it going to want to flex most in the middle of it's sides...the X really doesn't help much since it's just reinforcing the corners that really don't need it.
BTW, I wish I had SolidWorks, that plywood looks great.