I am installing a shower stall in a basment bathroom that was here before I moved in. the floor drain is already in concrete and the walls are already there. My question is all the shower stalls I have found do not have the drain in the right place to drain straight down. Can I build up the shower stall and put an elbow drain to connect to the floor drain that is in the concrete now? And if so where can I get some information on what to use to build it up? The shower stall is a brand name stall and pretty well built that we like?