Hello again, we finally agreed on a pool, and it's I'm my garage now. It's a Blue Wave Riviera 27x52". I'm starting to prep for the install and have questions. I am aware of the leveling and all, and understand that the frame and feet must be on the ground. So what is the need for sand or crushed rock base? Also, is the foam cove needed? It was not included, but is highly recommended in the directions. It came with steps, and filter and pump and skimmer setup.