I've had a few different sets of fairing speakers, and have R&R'd them too many times. I pulled the fairing only to find the left speaker was missing all the screws except one, the holes must be worn out. Short of buying new adapter rings, is there a way to tighten up the hole using the existing screw size? I realize I can go up a size but that's my last choice. Is blue Locktite good on plastic?

 

Go online to McMaster carr and look up plastite screws then get the correct size for your job, these screws are made just for plastic and they will not back out or loosen up.
these are the best for your application.
I used these for my amp when securing it to my nylon plates,they are a special tri lobe design.
McMaster-Carr
click on the link above it will take you right to the correct page.

 

I've used this method once before on a car...