Most receiver hitches on 5ers are not designed to tow any appreciable weight and are also limited on tongue weight.
One solution is to have the manufacturer install TWO, 2" receivers and then a hitch attached across both.
You also need to remember that just because you can tow double and 70' in your home state, you have to follow the laws on the state you are towing through. Texas max length is 65', some are shorter and some do not allow double tow. Other states only recognize you drivers license and then you follow their speed limits and towing restrictions for length, width and weight.
Personally, I will not tow behind the 5er. As a minimum, I would have a rear view camera on the back of the trailer as well as a tire pressure monitoring system to keep and eye on what you cannot see.
Ken
