Q for countertop experts: adequate support under stone table top
I have a somewhat techncial question for any of the countertop experts. I've had a table base custom modified to hold a marble top. The base is pictured below. I'm trying to double check the design to ensure any issues have not been overlooked, and that the support structure is adequate to support a 2cm laminated marble top (on a plywood subtop).
Here are some key dimensions. The edges of the table will overhang the nearest support edge by 7 inches, on all four sides. This means the corner diagonal will be nearly 10 inches. The main cross supports are 2 in tubular steel. The perpendicular supports are 1 in tubular steel. They are spaced at 25" in the long direction (perpendicular to the main bases) and 16 1/2" in the shorter direction.
The base itself has main supports of 2 inch tubular steel and should be adequate for the weight load. (The table itself is 42x54 and should weigh less than 250lbs based on 13lb per square foot for materials and 2.1 lbs per sq ft for the subtop).
The breadth of the base and the main 2" tubular cross support are designed for stability and to avoid tipping issues.
My main concern is on the cross supports and the overhangs. Will I need additional steel bracing in the subtop? I am basically seeking 2nd and 3rd opinions on the original design.