I don't know how close the geometry on my Schwinn Classic 3 is to the old Schwinn Heavy Duty, but I used to routinely load the Heavy Duty up with 200# of newspapers for delivery.

I had the Wald GB157 on the front and the 535's on the rear with a large shoulder bag sitting on top of the rear baskets. It was a very stable bike loaded. I was a skinny kid an at that point and weighed just under 100#.

Aaron