Very rarely will tightening the spring remove enough sag to prevent the water from pooling on long slide toppers. The fabric gets a little saggy. Even replacing the fabric only solves the problem for a few months. I would just learn to live with it or stick something like a beach ball or PVC support to hold up the fabric will stationary. The simple way to see if tightening the spring will help is to get up on a ladder and use your hands to twist the roller tube pretending to tighten the fabric. Usually, the fabric will be tight in one spot but saggy elsewhere. Tightening the spring will not help the saggy spots.