I would definately do what your initial thoughts were and what mglavin said about putting 2 servos on each elevator. This is a large plane. I am building their 39% 330L right now and am putting 2 per elevator, 4 for the rudder, and 3 per aileron. I haven't ordered the servos yet but am planning on using either JR or Futaba and use a matchbox.

My Edge has 1 5945 per elevator and I wouldn't want to have any less torque on it. It flies great though

Good luck
John