I have been hired to build a custom tub. It is approx 6'6'' long i need some help designing it.I am curious how do you get the liner to hold water if i have to install durock over it and then tile.? if you have any insight it would surely be appreciated by myself and my wife. I stay up at night trying to figure it out. I have built several shoewers but never a complete soaker tub the customer wants it to be in a surround with radiant heat running around the perimiter and 12x12 tile all around the tub base sides and surround. the tile part is easy i need insight as to the actual construction of the frame,liner,durock /or other base for tile and drain assembly many thanks for any help sjj