I've now got the 60mm box section. Its 5mm thick and bleedin' heavy. Should be idea for the table frame.

Appreciate any thought of reinforcing a 2000mm unsupported span. The difference in cost of the 2 designs would be minimal due to the cost saving with only one ballnut mount will go in to tooling plate. I've been quoted £160+vat for 2000x150x25.
Ta