You might want to try something on that twin deep vee. Instead of steering the engines and having to use a monster servo and battery, consider locking the motors straight and using an inboard rudder. Locking the engines is no big deal. Just run short 440 rods through the transom just far enough to locknut and washer them on both sides. You might have to move the rudder to a couple different positions to find where it works best. Just a thought.
Mark