T
Time's Ran Out
Ive always used 9/12/18 ml plyboard.
Does the job. But would depend on how much slack you have to get a finish
No need for fancy fittings in my view.
I just finish this job with 5.5ml ply. Screwed 3 baton Boxes behind to make more rigid.
Turned out as in pic
View attachment 101177
5.5mm plywood is too thin to tile on and certainly no need for fancy fittings there!