Here are some real world figures.
* 2011 F-150 Max Cargo from door jamb 1411#.
* 2010 Dutchmen Lite 25 ft. TT. Dry weight 5004#. Loaded for the road and across the CAT scales the TT weighs 6200# with about 750# on the tongue.
* That is about 12% on the tongue, the WD hitch is set a touch nose down.
The wife and I plus the dog and camp gear come to about 650#. This puts the truck at its limit. We have no issues towing, the E-boost pulls nicely and we have managed 40,000 mile in about 5 years.
Our trailer weight actually varies with the amount of "stuff" we need from trip to trip. Water, consumables, and gear can vary 200 to 300 lbs.; even more on weekend outings.
We love the rig combo but anything heavier would require a larger truck. Towing at the limit does take a toll on shocks, brakes and tires. Of course not everyone is gong to tow 8000 mile a year across desert and the Rockies.
Good Luck