We're about to embark on a total bathroom refurb and my wife wants to install marble mosaic tile flooring like she saw on a DIY show. What I need to know is what type of underlayment system is recommended for a pier and beam foundation with 2x6 T&G subfloor over 4x6 beams 48" O/C? The tiles will need to transition to 1/2" solid wood flooring in the bedroom so I want to keep the height to a minimum. Oh yeah, and she wants to but a freestanding tub on top of it, too! You think any of this is possible?