My "Bluebird" (at 1:12 scale)built from the 1991 MB "Super-Plan" has 2 rudders, 2 motors and 2ESCs. Running off a 6v supply I can use 1 battery per motor. At 1:12 scale (50") the total weight has to be under 20lb....hence 6v as the batteries are smaller and lighter than the 12v things. still gives ample running time.
If you choose the single rudder option but retaining the twin screw set-up I would advise having the props turning "inwards" to give better flow over the rudder. With the twin rudder set-up, she will turn on a "sixpence". BY.