3D planes tend to purposely have their C.G. set further back.

This let's them perform high alpha maneouvers such as hovering and harriers with more ease.

With a 3D plane such as your UCD, you want small "stepping" of the servo for maximum fine control during landings.

However this contradicts the manual's recommendation of long servo arms for maximum surface movement.

So what you do is instead, set the servo linkages up for maximum mechanical advantage, (1" arms or less) which gives you "finer" control, then offset this by setting the endpoints for maximum travel on the servo itself.

You would be attempting to make the servo "turn" further to it's extremes to get the same amount of motion out of the control surface.