We just made a 9x20 table out of 4x4.120 steel and made sliders. All the pics I have are to big but if you look on my website under the caddy you can see the new table it is nice. Dont weld it solid just solid enough not to brake and that will keep the warpage down and make it out of decnt thickness. We don't like the surface plate cause you coony get under it and around it. It is like working on the floor. Just my 2 cents
www.ironworksspeedandkustom.com
Rodger