OK so that should hold it there. Meanwhile, do you think the fiberglass itself plus the "backing" it gets from being in direct contact with the car's side panel will make a sturdy enough enclosure? I'm thinking about vibrations and resonances (not standing waves though, since there are zero parralel surfaces on the inside of your enclosure so I think those won't be an issue). Is the baffle reinforced other than the mounting ring for the woofer? I don't know how such enclosures are typically designed. Yours looks elegant with the carpet.
The enclosure is approx. 1/4" thick with flatter areas having extra fiberglass layers. The baffle just consists of the ring and fiberglass so Im hoping it's enough. Again, this is my first attempt with using fiberglass and making a sub enclosure. I can add sound deadening to any areas that vibrate too much.