I always consider ONLY the trailers GVWR when fitting trailer to truck. Anything else just doesn't cut it. Empty weight is useless as NOBODY drags around a completely empty trailer. Tongue weight is also a factor but I don't go by partially loaded weights there either. I use 15% of the trailers GVWR so I factor in the worst case situation where the tongue is the heaviest it will ever be. From there I see how it fits with the full factory ratings for the truck. My safety margin is not any 80% rule etc. but using the worst case figures up front.
Good luck / Skip