Hello, just got to a wet room job and the tray Is fitted and water proofed but the floor is way out at the entrance of the room. 17mm out. They're having 60x60 rec porc. My issue is whether I can Chuck some self leveller on to of the waterproof to build the floor up. But this would make the falls in to the tray even steeper as it has to meet flush with the drain. The builder says the customer is a pretentious nightmare lol