I too have been considering whether to get a toad braking system, what with the car I intend to pull behind my new RV weighing under 3000 pounds. And I'm satisfied that in most places I'd be legal without one. But in my case (I have an Allegro 32SA with a 24,000 pound GVWR and a 3000 pound CCC) in use my combined weights will be over my GVWR and in my chassis manual Ford says to use supplemental brakes when the weight of the RV and toad exceed the GVWR. So I'll use the machine as intended by Ford, whether legally required or not.
I was prompted to refer to the manual by a previous post in this thread.