Well 6 pages of statistics and opinions makes for interesting reading.
But I am from the CAT scale school. My 5000 lb. 400 lb. dry weight TT crosses the scales at 6200 to 6400 lbs. and up to 650 lb. on the tongue, when loaded for the road.
I am at or very near the 1411 lb. Max cargo limit on the door sticker of my 2010 F150; by the time I add people, a big dog and stuff I cannot live without in the bed.
After 8 years and 53,000 towing miles From crossing the country three times, through the Rockies and Smokies, desserts, ice storms and high cross winds, our 25 foot Dutchmen has been through a lot.
And yes, towing at, near or above the truck limit does take it's toll on shocks, brakes, suspension, tires, etc. plus seemingly endless tweaking and repairing of the TT.
In all my travels and discussions with other RVer, very few know or care about the truck ratings. If they like the way the rig handles they keep it, if they do not they buy a bigger truck.