Additional tension can always be added to the spring or springs. But here is what I normally run across.
Customer complains that the topper fabric is loose. I take a look and the fabric is tight in the middle but loose on the ends and flaps in the wind. The end fabric has been stretched. If the fabric is tight in the middle, adding tension will not help the ends. It just makes the slide motor work harder to get the slide out.
As a test, get up on your ladder and grab the fabric roller. Try and turn the fabric tube to simulate a tighter spring. If this solves your fabric sagging problem, the add more spring tension.
