Put 320lbs on one of the new black carts the other day. The whole back of the cart bent about six inches, getting it off the ground. Pushed it throught about 25ft of 4" deep snow, wrestled it through a steel walk-in door, about 180' of warehouse travel, (because they wouldn't answer at the loading dock.) When I set down the load, the back of the cart again turned to rubber, flexing 6-8inches.
Better, not bigger!