interior plastic modification help

[BulldawgMusclecars]

If I'm understanding correctly, you basically want to install kick panel speakers in the existing holes, and cover up any other holes in the plastic? The easiest way to do this would be to figure how much spacing you need for the speaker, and glue MDF speaker rings (available from a stereo shop, online, or make your own) to the plastic with epoxy. You can then stretch some old t-shirt material over it, and glue it down with 3M Super Spray Trim Adhesive. Once it sets up, paint it with fiberglass resin. It may take several coats, with drying time in between, but eventually you will have a sculpted-looking panel that is hard enough to sand. You could sand it, fill (with standard plastic filler, like Bondo or Rage), and paint it if you wish, or coat the back of a piece of stretchy, automotive grade vinyl/leather with the same 3M adhesive and stretch it over the panel. Hold it in place with small clamps, or even clothes pins will work well, and let it dry. Sometimes it helps to heat the vinyl a bit with a heat gun. Once its done, cut your speaker opening in the vinyl, install the speaker and trim ring, and its done. I'll upload some pics of an example I did, if I can find them.