RVs are the most difficult type of trailer to tow. Big sails that catch lots of wind, relatively light for their size as you are mostly pulling a box of air. A 5000 pound travel trailer will be a lot more work than a 7000 pound boat. TTs typically hve higher % of tongue weight than other types. People the RV tend to take more people and stuff because they are living in them instead of a boat or flatbed trailer.
You will likely be payload limited first with the Durango. If you have 1400 pounds and the family weighs 500 pounds and you don't take an ipod to entertain someone while traveling, then you have 900 pounds left for trailer TW. That's about 7000 pounds loaded RV, under 6k dry.