You should preload the springs. I'd say 30-50%. You may need to add a separate control horn for the springs. Usually they have a triangular one that screws to the bottom of the rudder. That way you can pt it where you want to get plenty of tension on the springs. It doesn't take much to turn it when you're moving. I'd never go direct connect to a servo on a bigger plane. You will trash the servo in no time.