Andy,

Servo positioning systems are often used in my profession, so let me explain.

As long as the needed torque is less than the max the servo can generate the speed will be (nearly, loop gain!)) the speed of change of the input, so the limited speed of chance of the output of the transmitter channel.
Limiting the speed of the servo will reduce the needed torque of the surfaces so the modern servo will be strong enough.
In the past the problem was the limited generated torque of the servo. I still remember we did use AC127 and AC128 or AC187 and AC188 germanium transistors and 2,4 V to switch the power of the servo motor. It all was a little bit limited!! For that reason it was better to use one servo and I still do.
Pro is, the ailerons always are synchronized!!

My transmitter is FM modulated, not AM but that does not has influences on the flight characteristics just as the other points.

The car: Chevrolet, so “All in style”


Modern see post 1954:
http://www.rcuniverse.com/forum/fb.asp?m=9590120

Cees