I am in the middle of a remodel of the master bath. I have a Kohler shower receptor (pan) that is ready for installation. I have relocated the drain, trap (ABS). The trap aligns well with the pan (not glued up yet). The Kohler install instructions say nothing of laying a mortar bed under the pan is this a necessity? Is thinset mortar OK for this purpose, and how large should the mortar bed be? Also, the brass fitting in the pan has been installed using silicone under the flange, the rubber seal and then the fiber seal on the underside all tightened up. Does this sound correct? This is a second floor bath with no access from below.