Hi!
No, No ! you must have missunderstood the whole thing...the throttle servo must be set up so that it doesn't push against the throttle more than is necessary, that means the throw of the servo must be adjusted properly. This is easy with todays servos as end point adjustment is done electronicaly. Even before modern computer transmitters came along it was easy...you just matched the right lenght of the servo arm to the right lenght on of the throttle arm so that the throttle opened and closed precisely the way you wanted. No spring is needed!
Regards!
Jan K
Sweden