As you can see on the example above, it is very important to use as much of the servo travel as possible. Increasing the travel by 10 degrees here drops the torque requirements by 60 oz-in.
Also note that the simulation was done at 60 mph. Increasing the extension speed will dramatically increase the load on the control surface.

Finally I have edited the link to the imperial units file ( the .xls extension was missing in the link ).