As always, I can only relate personal experience with "the numbers".
the truck:
1994 dodge Ram CTD 3500 dually. the GCWR of the truck, according to the Owners Manual: 18,000 lbs.
the Trailer:
1999 Monaco McKenzie 32 foot triple slide fifth wheel.
Full time living.
the scale weights:
UNDER GAWR, all axles.
UNDER GVWR, truck and trailer.
OVER truck GCWR by 3,180 lbs.
It crossed the Continental Divide several times, crossed the Sierras a couple of times, and the Cascades a cou0ple of times.
Nothing bent, nothing broke, there were no accidents, nobody was injured or died.
The Motorhome:
1995 Tioga 29 ft. on an E350 chassis, 460 V8, 3500 lb. hitch
The toad:
2006 Jeep Wrangler Rubicon Unlimited, mildly modified, weight unknown, on a fixed arm adjustable width 5000 lb. capacity tow bar.
A well-qualified local welder reinforced the hitch.
The Jeep was towed "over the mountains and through the woods" several times.
Again, nothing bent, nothing broke, etc.
If you look at nearly anything, you will find at least two "ratings"; the working rating, and the failure rating.
Chain, cable, steel bars, bolts, plumbing, hydraulic hoses, etc. ALL have both a working load and a failure load. When it comes to vehicles, the manufacturer will never give out the failure load of any part. That lack is probably quite justifiable! The fact remains, the stated working rating is carefully determined to be that load at which the chances of failure are statistically insignificant, in order to minimize the liability of the manufacturer. the actual failure load can be 50 to 100% higher than the stated working load. The user will never know, unless he breaks it.
So, do I recommend that the working loads should be regularly exceeded? No, of course not.
Do I think that paranoia exists when it comes to ratings? Yes, based on a lifetime of experiences hauling and towing, I think it does. The continuing threats of legal action are quite humorous, however, considering the likelihood of ever seeing the threatener, and the even smaller likelihood of being in an accident with the threatener.
The bottom line is, it is YOUR rig, do it YOUR way, being as safe as you can, and Good Luck.