We are replacing a standard toilet with a rear discharge toilet. Previously, the floor was built up by about 6 inches on a wooden platform, with PVC coming down then an elbow to the drain which runs parallel to the floor about an inch above the concrete floor. I see most of the rear discharge toilets have the drainage hole around 3 to 6 inches above floor level. My question is should I use 2 elbows to connect the toilet to the drain, or can I use a flexible single piece, since the drainage will come down from toilet to drain.