Sorry for the long wait on a response. I have a steel fabricator make a t-shaped piece of metal that I secure to the studs before we start tiling. I usually draw it up for them. It's not something anyone has been familiar with so I always have to explain its purpose, but that seat isn't going any where in an earthquake or regular movement. It's as sturdy as t can be. If you really need help explaining it to someone, let me know and I'll send you a sketch.
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