I am about to start my 20x40 vinyl liner type pool.... I plan on pouring cement in the shallow end but do I have to make the deep end out of "dry pack", or pool krete?? Can it just be sand?? No one will walk on the deep end so it should stay smooth.... I have heard of people that have the entire floor bottom out of sand... So I justcwanted to get all of your thoughts on this... Any info is appreciated!!! Thanks!!