To move the cover down, you can't just grab it on the end and pull on it, or it will tighten around the core (think chinese finger puzzle). You have to grab the core, and push the cover down a couple of feet, then grab the cover and core below where it's bunched up and work the slack down - like milking a cow. Repeat these steps until you've moved the cover down 25'. After the tapered core is in place continue to work down the cover removing any slack. The cover must be tight around the core to develop good cover to core adhesion, otherwise you'll have problems with the core slipping inside the cover at the cleat location.