I want to mount a three bottle soap dispenser in the shower. The surround is fiberglass, and I have the option of gluing or screwing. A tube of no-name 'silicone glue' came with it, but it is 'made in china', and I have no confidence in it, so I would use epoxy. If I glue it, I worry that the weight might rip the fiberglass open, or just not hold at all. If I screw it, then I need to open the other side of the wall (in a closet) to add a brace. Toggle bolts crossed my mind, but I would have to drill large holes. Suggestions?