All that, and nobody pointed out that on the off chance the OP were ever pulled over and weighed in the United States, or on the off chance that he was in an accident, the law and lawyers would only concern themselves with his REGISTERED weight, which can exceed the GVWR by thousands of pounds. I don't know what the states use for criteria on the limits, but from what I am finding it's pretty much whatever you want to pay for, possibly up to 32,000lbs, 20,000 for the dually axle and 12,000 for the single axle.
Obviously you're pushing things if you exceed the combined weight ratings of all your tires in all positions (except the spare, duh). The combined GAWRs seem to be a common choice. Large trucks are rated by their combined GAWRs, yet pickup trucks have a factory GVWR that's often thousands of pounds below the combined GAWRs.