I suspect there is a huge gray area between what is recomended/safe and what you can get away with. How smart that is, is completely up to you.
Dry weight for a 2619 is 2673# and a 2720, 2742#. Check your vehicles payload capacity then deduct passenger weight, all your stuff, tongue weight, propane tank weight, fuel, etc.... Then look at you vehicle's GVWR and see where you're at. The following website is pretty good.
http://www.rvtowingtips.com/index.htm
My own rule of thumb is that you don't want go over 80% of any your rated capacities. And lastly.. how far are you going how often.. ?