Need brakes on boat trailer?

We have been towing double since 1993, only the first boat didn't have brakes, a 19' Bayliner Capri. It was very light. Since then, every one of my boats have had tandem axles and surge brakes, since 1996 and I have never had a problem with the surge brakes on any of the three boats, either going up or downhill. I believe the surge brakes actuate when there is significant pressure from the boat trailer forward to cause them to start working. Going downhill with the engine braking system does not seem to actuate the brakes so I am going to keep towing double with electric brakes on the FW and surge brakes on the boat trailer. In Wyoming, the max length that can be double towed is 85' and my outfit measures about 71' so I'm good to go. I don't know about any other states around here as I haven't towed double in any other state than Wyoming. Some day I might and then I will check to see what I need to do.