You could get away with twin transmitters but, to do so, you would have to have twin receivers and battery packs in the boat. You could use the same servos for both receivers, just put in a "Y" adapter between the servo and the receivers. The one drawback to this would be you would need to set up a switching system to turn the unused receiver off to prevent the two from fighting as one is in failsafe while the other is trying to operate the servos