I had a brand new Y-harness with reverser by futaba last summer for a new 1/4 Extra that had dual elevator servos. I'm not sure if it is only designed for 4.8 volts, or what pack I was using for that matter. I use a 6 volt pack now, but during the time of set up, I think I was using a 4.8 pack. Anyhow, right after I got it all set up right, I was tieing my wires in so they wouldn't move, and it went dead....I don't think I even pulled the wires that tight. but if it had failed during my maiden flight, I would have been very upset. I took it off and mixed them on the ailevator menu. Futaba sent me a new one, I am saving it to use for my P-40 on its flaps.
If your still working on the elevators, you could tie the elevators together, making sure the hinge line is in-line, else they would bind, and ganging 2 servos together using a servo to servo to pushrod setup, or just going for one of futaba's $35 1/4 scale servos. You would loose the independently adjustable feature, but it would be ok as long as you took the time to make sure everything was lined up. If you Y-yoked split elevators together,and ran a single pushrod down the center, (regardless if it were to 2 servos or 1 big one), you have to watch that the pushrod doesns't move from side to side, otherwise it will yank one elevator up and down more than the other, which is what your trying to avoid in the first place. A fix for that being the case, mount the servo on it's side, so the vertical arcing woun't have any change in the pushrod's geometry. Any arching becomes more drastic the more throw you have. So keep that in mind. Happy Building!