I plan on installing a mortar bed shower pan with a liner in it. The one thing I'm curious about is the finish mortar bed. After pre-sloping a mortar bed beneath the liner, do I additionally need to slope the finish bed or can I put in a 1 1/4 inch layer following the slope of the previous bed? It seems to me as long as the finish bed has a 1/4" per foot slope that should do.