However those diagonal struts will mean you cannot put any long jobs sideways on the table. I have a small fixed gantry machine and it's nice to be able to put a long piece of stock across the table and work on it, even though the "throat" width of the machine might only be 6 inches that still gives a lot of options for cutting long pieces of wood or signs etc.
I know that was one of the cool and attractive features of your design (sorry!) but based on that last diagram I would lose those thin struts.
I think you are right. I am redesigning the side plates as we speak. I thin I will add a rotary axis (http://www.cnczone.com/forums/diy-cn..._8_a.html)that can span across the center of the machine. I would rather have the ability to do rotary milling & indexing more that oversized stock.