I just replaced my electronics and decided to switch to a mounting board instead mounting the transducers right to the haul. I installed everything myself and the board I purchased was desinged for this application. I did screw mine to haul. I just put silicone in the holes and it sealed everything up. Boat doesn’t leak a drop.
By using a board you can adjust your transducers without putting more holes in the haul. I would definitely suggest going with a board.