Structolite mixing for bathtub mortar bed
i used to make mine a little weaker than peanut butter. if you do make it this stiff then you'll have to apply more pressure to seat it. i didn't look up the fixture number on what you have but most tubs and showers today comes with wood bracing embedded in the fiberglass (if it is fiberglass or acrylic) and require no extra support. if not done properly this extra mud will create a hard ledge in places where a crack can form where the mud ends. my supply house will provide clients with an instructional sheet to do this if it is needed for some reason but they advise against it, if not needed. we did this years ago when fiberglass tubs first got popular but the industry evolved away from "mudding" over the years.