Actually, #1 weight was the heaviest on the normal frame Fox guns. However. the HE and Sterlingworth Wildfowl 12 gauge guns both came with 0 weight barrels. These were both made with wider frames to accommodate the heaviest barrels offered. I'm not super technical, but I'm sure the width of the frame is readily available, probably in McIntosh's book.

My HE has 32 inch 0 weight barrels and weighs 8lbs.,11.9 ounces.