When I was doing custom stereo work, I came across the same problem. Nearly ALL of the tabs were broken (in my opinion to poor design). After using several different methods including fiberglass and plastic welding, I realized that the tabs broke for a reason. PLASTIC SHOULD NOT HAVE BEEN USED HERE!! Anyhow, I purchased some sheet-metal tie-rods that used to brace the underside floor joists in a house. After hammering them out so that they were flat, I then bent them to align them with the original tab points as well as the screw points used to hold the trim in place. Kind of hard to explain, but I hope you get the idea. These new taps are bullet proof and now I can slam my car door with no worries of broken tabs.