Ok so I could just about fit 2x 12.5mm if I squeeze the bath into place, but assuming dot and dabs will add a cm or two onto this, I can’t fit anything 12.5mm in place, unless I only board down to the top edge of the bath. I assume this is a terrible idea and opens up to water ingress significantly.
Would 6mm tile backer boards suffice on the walls to hold tiles, or are these a bit too flexible?
I’m getting a distinct feeling I’m going to have to take out one end wall and build a stud one instead, just for the sake of a couple of cm!