I installed a 21 X 43 foot AG pool 2 1/2 years ago. It has a sand base under the liner and the sand has all sorts of irregularities and bumps and along with the sand cove also breaking down it is a nightmare to clean and looks bad on a nice sunny day to boot. I want to drain and remove the liner, which also has many wrinkles, and put in some sort of firmer base. What is the best recommendation for an AG pool base? Poolcrete or foam for under the liner? Or something else?