Here is my experience.
The TT manufacturer's spec sheet for my specific unit which came with the manuals said Hitch Weight was 412lbs. I had 2 20lb propane tanks, and 2 batteries. When I weighed the tongue it weighed 700lbs. This was ready to camp with the exception of any water in any of the tanks. It also did not include the 80lbs of WDH.
Total weight without any water was 775lbs or 55lbs over the hitch rating.
My Dodge Durango had a maximum hitch capacity of 720lbs because of its uni-body construction. Some vehicles hitch tow ratings increase when WDH is used. This was not the case with mine when I talked to customer service at Dodge.
As safety is very important to me with a family, I traded my Durango for a tow vehicle I knew would safely handle all the weights associated with my TT.
I know some may say it was close enough, but I'd rather have a reasonable safety margin than be on the edge.
I would recommend weighing the hitch to make sure it is within the safety margin for your tow vehicle.
Good Luck