Hey there! My 18ft above ground is about to bite the dust so I'm considering building a semi-inground flat bottom (due to high water table) build with cement blocks and a sand bottom. Would I be able to use an above ground pre-made liner (12 x 20) and build the pool to fit the liner? It would keep initial cost down and future replacement easier. I'm still in brainstorming mode and weighing out different construction materials and techniques. Any input would be greatly appreciated!!