Shower Waterproofing

Long story short: went to regrout old shower and found mildew and tore the whole thing out and found localized mold. No waterproofing anywhere; tile on concrete basement slab, tile straight on cement backer, and horribly out of plumb.

Anyways here I am a month later and am almost ready to finish off the waterproofing. I had this idea to create vertical thresholds with 2” kerdi to give a visual break in the bathroom, and also to allow me to eventually redo the remainder of the bathroom (didn’t want to bite off more than I could chew at the moment).

Here I have what might end up being a tricky area to get true 2” overlap. Any ideas? I plan to use kerdi band and corners as best I can, then cover with several coats of hydroban.

Thanks!!