Matt
Good guess! The overall structure is 48w x 48.75d x 18h before I applied the .125" plywood.
I intentionally made it so that it overhangs my 48"d table by .75 in the front because I want to add a decorative front rail to the table.
You end up with an inside area of appx 46.5 x 47.25 x 17.25, which should just fit a 1000mm x-carve plus cable track