You hit on the part that most never consider > tires and their rating. Read the sidewall and see what the max load allowed is. I once long ago loaded my F100 with 3400 pounds of coal, like a stupid fool, and drove about 40 miles to my house. When I got there, I couldn't even hold my hand on the tires, they were so hot. Like I said, STUPID FOOL. Never again.
Also, two stacks of them is just begging the state or local police to increase their revenue at your expense. Sure it was your buddy, Mr. Macho, who volunteered but would he be your buddy after the fine and possible confiscation of his truck? I really enjoy laughing at these ego-boosting moronic threads that pop up all winter long!