I had a metal frame at one time and used a Dremel to notch it. I began to notice a rattle from the back and couldn't figure out what it was. Eventually I removed the plate frame, but I was sure that couldn't possibly have been it. I couldn't imagine I'd even hear that if it vibrated a little and only tried removing it because I was at my wit's end on what else to try. Well, they say sound can travel through a vehicle in weird ways and apparently that was it because the noise stopped and never has been back since I took it off. Mine was metal and was just a frame, so maybe your plastic cover will not do that to you.