Just my experience : I installed my aboveground Intex 16' round pool a couple of months ago and used 1 1/2 inch thick styrofoam sheets under the liner. After leveling the ground, I just laid the styrofoam (4 x 8 sheets) down on the ground - taped the seams - put the ground cloth over the top and installed the pool. Feels very smooth and cushy underfoot. The styrofoam only cost me about $50.00