We have purchased a drop in whirlpool tub for our master bath renovation. THere is an adjacent wall on the long side of the tub with 3 picture windows 12" up on the wall. Our contractor insists that for him to ensure waterproofing, the cement board and tile need to come down onto the top surface of the ledge of the tub. - this would make the long edges asymmetric and not look as nice as having the tile end on the outer edge of the ledge. Second, would you tile up to the bottom of the windows, or further up between the windows?