My instructions don't talk much about tension, and I think that's where my problem is but I'm unsure. How do you set the tension?

When the rudder is neutral, cables are snug but not overly tight. When I input left rudder, both cables end up loose, and the return to neutral is very jerky. When I input right rudder, both cables remain tight throughout the range of motion, and it is very smooth and accurate. There is enough tension however that the surface the servo, battery, and receiver are mounted to flexes with right rudder, though not too bad.

What do I do? Here are some pics of neutral, left input, and right input, respectively. You can see that the servo horn has a slight amount of Ackerman as the connection points are aft of the center screw. The lines cross inside the plane.

Please help!! Thanks.