my buddy has a ski boat. And on his trailer, right side, by the hitch there is a pin/plate to block the surge bolt from moving back wards. That will inlock his surge brakes to back the trailer. No need to mess with the wiring
But if you can just do it with the wiring and never have to worry about getting out and blocking off the brakes when you want to back up, doesn't that make a little more sense?