my back plate holes don't have metal threads (that I can see), just plastic, and one of the holes feels like it is stripped. Should I drill new holes offset from the old holes (or stick to the dimples)? Or is there a way to get behind the plastic to add a nut to the inside to firmly secure the plate?
BTW I only tightened to a point for firmness and didn't try to over tighten them understanding I was securing it to plastic and the threads were holding the screw in place.
Really? I just went outside to make sure and there is indeed metal threads for the back plate. I wouldn't recommend drilling another set of holes in the back, maybe find a larger screw to get it snug or as a last resort they sell these compounds like Quiksteel that when dry you can drill into and take it from there. Let me know how you make out with that.