His truck is licensed for a given weight - GCWR, axle weights, payload/GVWR. Exceeding them breaks the law- you need to pay more for your registration in almost every state. Running too heavy is illegal, be you a commercial tractor trailer or prius.
And it's unsafe. Not just for you, but everyone on the road.
And you never know what local event may cause the cops to get 'enforcement happy'. A few years ago here a guy on the way to work didn't have his safety chains on , the trailer came off crossed the yellow line and killed a dad and his 3 kids in their minivan, then a flatbad came loose killed a couple of more
and then this one here also
So yes, the cops here to set up trailer safety check points and DO write tickets.
And every insurance policy has a line it that they are not obligated to pay if you are breaking the law.
Sure, at high noon in may on a level road there's not likely to be cause for concern. Add in rain, darkness, hills curves and it can change. Add in any emergency stop or swerve and you may end up in the median upside down (which I've seen more than once).
So with an overweight combo you'll take 30 feet longer to stop. Ever had to stop fast? What if you had to take 30 feet more to do so? Would you perhaps have hit the thing in the road? yep, THATs teh issue right there.
Why does a silverado with a tow package have twice the tow rating of one without, same engine, tires, transmisson? Why does even a base 2500 have as much as a 'properly equipped' 1500? You're not an egineer so you don't know. To just assume it's the liability lawyers or EPA rules or some such is a guess - a guess with your money, possibly your life and others.
Do you know the difference between genius and stupidity? Stupidity knows no limits.
The OP will do what ever he will do - we can't stop him. For the $500=1000 a year he may save in gas he's likely to spend it on repairs instead. It would probably make more sense to go buy a used gas sipper car and have 2 vehicles.
Our expy was a third vehicle used just to pull the TT - cost for a year, for registration, inspection, insurance was about $200. A transmission can cost 10 times that easily, if not more.
What price a white knuckle ride?