My SO3 XXL used to sit on a table that was solid. However the center of the bed sagged. I had put a block of plywood under the center and that helped.
I made a torsion box to put on the table top and then removed the leveling feet and put a piece of 3/4" rigid foam between the torsion box and the SO3 frame. The sag was gone and the upgrade was a good one. No CNC can be at its best without a solid foundation. My plan for making a torsion box is on the forum. The torsion box would be a cheap solution and even if you later upgrade to a more solid base plate for the SO3 the torsion box would help support a heavy load.
torsion_box.pdf (2.0 MB)