Preslope under cultured marble base?
I am having a shower installed in my basement. The shower is approx. 2.5' by 4'. I am having an cultured marble type of material installed in the shower. It is 3/4" thick on the base and 3/8" thick on the walls. The installer indicated that he wants to wait until I have the water-resistent drywall or cement board installed before he proceeds. He would then come in and install a vinyl liner directly on the cement floor (no pre-slope) and the vinyl would not be behind the wall board. He then puts down a bed of mortar and install the preformed presloped cultured marble base and glues the walls to the wallboard. Is this going to last or am I just asking for trouble?