You are right that the states do not enforce the manufacturers limits. But I can't agree with your logic that that means that it is perfectly OK to overload.
Tire manufacturers set load limits for their tires.
Axle manufacturers set load limits for their axles.
Truck manufacturers set load limits for their trucks.
But IMO, it doesn't make sense to say that since the state will allow me to purchase a tag for huge load, the load limits set by the manufacturers can be dismissed. Does the state know more about the product than the manufacturers?
Are the limits set by the manufacturers conservative? Certainly. They reduce their liability by rating their products conservatively. Prolly a good idea these days:
From a buddy of mine RE a similar discussion on another list:
As in all things, there are shades of gray. I am pretty strongly in favor of following the manufacturer's recs on most things, esp. weight limits. Often, these weight discussions pick apart something that is perhaps 500 lbs. overweight. While I personally wouldn't do it, I don't see much harm either. Then there are the situations where we're talking a couple of thousand pounds over and starting to push the limits of max axle and tire weights. Now, I start to get concerned. The somewhat arbitrary max weight that the manuf. puts on for towing or max combined weight can be argued with. The axle ratings, and very especially, the tire ratings cannot be safely pushed or argued with. The medium level overloaders are pushing those limits and reducing their margin of safety.
Now we come to your friend's situation. His is not a gray area or borderline situation. Quite simply put, he's reckless for even attempting it. It will be overloaded by probably any numbers applicable to the truck. The truck is only rated at 20K combined and the trailer ALONE is almost that. I am not impressed by what "hot shotters" and others are doing. People do all sorts of dangerous things, that doesn't mean we all have to do them.
I was thinking about this situation while writing this and it occurred to me that there is a potential (before y'all go ballistic, I said potential...) criminal aspect to some of these overloading situations. I am a prosecutor by trade. The veh. homicide law in my state has a "reckless" prong that includes speeding, driving drunk etc. I once prosecuted (successfully) a guy who killed 3 teenage passengers in his car. Speed was one factor, but his recklessness in choosing to drive on that particular road under foggy conditions, dark, etc... were all factors I used at trial. Prosecutors have a lot of leeway in how they charge something up. If a set of facts came across my desk where a person knowingly went charging down the road with such a grossly overloaded arrangement and killed somebody, I would definitely factor the purposeful overloading into my decisions. I don't foresee anybody charged up for just overloading, but in a bad enough circumstance, I don't see why not. Just looking at it as a prosecutor instead of an RV'r, it is clearly "reckless" by the legal definition of that word. I did take a quick scan of the legal database and there is at least one case where a truck, overloaded with gravel, went through a stop sign and plastered somebody. The overloading was used as a factor. I'm not trying to scare anybody, nor am I under any delusions that the folks towing overloaded are going to "lighten up." Just some "thinkin' out loud" from an attorney. The fact is that in the legal world, at some point in the contiuum... an egregious enough situation CAN (not will... can...) move into the criminal arena.
Unless your friend lies to his dealer, he will be kissing his warranty goodbye as well. Tell your friend to get a medium duty truck like the F-550 or the FL 50-60. That trailer screams for such a truck.
So flagrant overloading can be an issue in criminal court. Guaranteed it can be in civil court. Good thing that the polo ponies were the only lives lost. They don't have lawyers.