First of all, thank you for all of your advice. I am closing my above ground 18ft round pool. First winter as a pool owner. I have purchased a winter cover, your winterizing kit and a roll of stretch wrap to protect the cover. I also have a 4ft x 4ft air pillow. I'm balancing and cleaning so I can cover it this weekend. My question is, after the water is balanced and pool is clean, should I use the air pillow to go under the cover and the stretch wrap or is it not necessary to use it? Illustrations in the box with cover do not show an air pillow being used.