I have found when driving with a trailer in the peoples republic of california (18 wheels, governed at 67), I could run at 67 as long as I wasnt in and out of lanes passing cars, the chp left me alone.
Here in nevada, I took a class with the dmv to be a cdl tester for my employer, and the people there said that those big rv's are now required to be driven by a non-comercial cdl driver and the rv/tow vehicle weight limits are starting to be more closely watched, which means that some 3/4 and 1 ton trucks arent big enough to tow some of the rv's out there. Dont know if its true or not, but thats what the dmv people told me.
John in Vegas