once you install the cement board (so that it sits above the tub flange), fill in that channel with thinset, and let it harden. once hard, go ahead and install your Kerdi, so that it's sitting no more than 1/8" off the tub. Then you can seal it with Kerdi-fix. That's the "book" explanation. If it were me, I'd use the same color siliconized latex caulking as my grout and seal it with that. Reason being that then you wouldn't have to worry about the color of the Kerdi-fix sticking out from under the tile.

Wow, thanks bumble doodle! Tt is great to know that the tub works well as a shower. We are tall too--at least most of us (two of my teenage daughters are twins and one is 5'2" and the other is 5'10", so maybe the short one complains a bit but that's ok, since she complains about everything!) We are getting the non-jetted version. Also, I am hoping that building the deck at the front will help with the water spray. I am pushing the tub back into an alcove under the window the long way (so we get into the tub at the 32" side rather than from the 48" side) and we are trying to go without shower doors in order to make the bath feel open. With a deck, we buy a few more inches of length to help avoid water on the floor. We may not succeed and will put a panel on if we have to. Any thoughts on this?

I know I've seen some sizable niches here in the past year or so. Do a search at the bottom of the page for niches and see what you can pull up. I'll post some pics of the niches in our three bathrooms. Our niche sizes/placements/orientations were based on various factors; shower storage needs, tile shape/size, behind the wall restrictions (pipes, wiring, studs....). Guest bathroom niche: Hall Bathroom niche: MB niche: HTH!

@jewelisfabulous - ahh, so nice to have a window! I'd like to hang artwork, but I'd be a bit concerned it might fall and damage our new tub! @monicakm_gw - thank you taking the time to attach a photo. What a serene bath tub you have! You just gave me a great idea for the 3 walls that will be bare since we won't be tiling all the way up to the ceiling. A towel rack would look great on the back wall :) 1. Did you mean your tub is 19" in height (from the floor)? 2. If it's not too much trouble, I'd love to see what your faucet for the bath tub looks like!