rowekmr, We often tow a 12' flatbed behind our 39' 5th wheel (Polaris Ranger,and gear for hunting or off road camping), or occasionally a 21'boat.
There are internet sites were doubles towing regulations state by state can be found.It varies from forbidden to fairly non restrictive. Generally, overall lenght dictates what you can/can't do. My rig is too long when towing double in many states, where towing doubles is legal.We would like to fish Lake Powell, but are too long for Utah. Will have to rough-it in a tent! :R Thankfully, we live in a state that is very generous with towing laws. Which, helps us enjoy all of what Wyoming has to offer. memtb