4' x 4' x 8" Router Build

[JAZZCNC]

I think I'm going to redo my frame design using 60x60x5 for the legs, 120x60x5 for the rail supports and maybe use 50x50x4 for the bed and triangulation / stiffeners.

I wouldn't take that route as the difference in steel price won't be massive. It will make welding more difficult because of your mixing different thicknesses and tube sizes.
At this width, the bed will be much less resonant with the thicker, wider tube size giving a better finish on parts. Esp when cutting harder materials that will resonate into the bed and frame.

Keep in mind it's the foundation of the whole machine. It really isn't worth spoiling the broth for apeth of salt.