I have been having the worst time getting the rear shorty 6 centered. My best guess is that the tension in one of the return springs is waaaaaaaay off. The only way i can get it close to centered is if i put the left tension screw all the way in and run the right one almost all the way out. They were both mounted on the same hole on the frame. Am i missing something? Where can i get just the return spring if my hunch is correct?