The servo for mechanical retracts works differently than other servos. It has two positions, up and down. It has no neutral. There are reasons they are like they are.

When one of them is either up or down, they do not draw current. And the rigging has them at full throw, so there is little or no leverage against the servo arms. They rotate 180degrees or thereabouts going from full up to full down. THEN they draw current.

Mechanical retracts are designed to complement those servos. The retract actually doesn't start moving the strut until the actuator arm has moved something like 15% of the total movement. The actuator arm is actually moved into a mechanical locking position when full up or fully down. The actuator arm does not have to hold the strut either up or down. The last 15% of movement moves into lock at either end of the throw. It all works like gangbusters.

Here is a picture of the retract servo in a Kyosho P40 Warhawk. It's a 46size warbird.