Note that we cannot talk about hidden linkages on jet models ( when the servos are in the flying surfaces ) because the speed and power requirements involved dictate for long control horn.
A typical value on a 1/6 th scale plane is a 1,5 cm/0,6 inch control arm.
So the control side of the linkage has to stick outside on non torque rod actuated surfaces.
Once again, please refer to the links above to see how to compute such requirements...