The key to using one of those without binding is to take the retract and measure the throw of the pushrod from down and lock to up and locked.

Lets say it moves 1" for simplicity.

Measure the distance between the holes on the servo arms or better yet, get a blank wheel and drill holes. You want the holes spaced across the arm exactly 1" apart from each other. (not 1" from the center of the servo arm screw)

Any less and the legs won't lock fully, any more and the pushrods will bind.