? Shelf/Drawer Liner for Shower Mat?

Yes it works just fine.

Did exactly that to the shower floor in the TC last fall, although it was for a little bit of warmth rather than as a shower mat. Works well to keep feet warm, but haven't showered in the camper since installing the liner. Our floor is smooth fiberglas but I haven't noticed it sliding , so I think your rough floor should hold it just fine.
Brian

Years ago the rental I lived we used a piece of the non skid you put under a rug. It comes in bigger pieces than what you are talking about and is a little thicker. You could just cut it to fit the tub.. You can throw it in the wash as well but dont put in dryer ..