Hi, I've recently started renovating my semi-ensuite however, i've run into the problem where I don't know if i'm to tile to the base of the second tiling flange on my double tiling flange alcove bathtub. My denseshield (kind of like backerboard) finishes at the bottom of the first flange, which is the top one, and then i have additional "flange" for tile, i suppose. Pictures as follows, I was reading in my home depot tiling book that I am to put a 1/4 inch shim strip and then tile resting on that, however I am not quite sure if this is correct, as I don't know if the bathtub featured has a double flange! help! this is urgent, my helper is leaving on Monday and it has to be finished by sunday!