I'm working on the base for my new 21'round above ground pool. My instruction say to measure from the center a 17' circle and dig out a basin 6 to 8" deep. Well after days of digging I found out I did not need to do this. I was just following directions. I wanted a flat bottom. My question is, I'm more in the 4-6 inch deep range.. Can I just fill with extra sand? And water and tamp it for a few days to get it to settle? Is there a max amount sand that can be used on the bottom? What a lot of extra work this has caused me. They should of told me this step was not needed. Any advice?