If you run your truck in tow/haul mode on down grades,the boat trailer brakes are being applied even if you don't have your foot on the brake. I have burned up some brakes and bearings in Utah / Wyoming go to the Gorge. The other key safety factor of electric over hydraulic style braking for the double tow is that one can apply brakes to the boat trailer manually through the controller should the boat trailer get into a wagging motion without applying brakes to the whole rig. That tends to straighten everything out. For definition, don't misunderstand "electric over hydraulic" as an electric brake. The master cylinder is simply controlled electrically and the cylinder back is hydraulic.