There's a lot of shotgun heat shields out there, some made of metal, others of supposedly indestructible polymer or "plasticote zytel fiberglass" (plastic fiberglass). I've heard of problems installing the metal ones because the parts don't bend quite right and/or scratch the barrel. Question is, does it really make a difference for us average shooters who aren't on a battle field and constantly rapid firing to get a plastic one versus a metal? What is your experience?