I doubt anyone has an answer as the Stevens is new and probably different from other guns. On the other hand, who knows? It is said to be a Chinese copy of the Ithaca 37 with some significant differences - like 2 action bars versus 1 on the Ithaca.
Have you thought of just shortening the LOP on your factory stock? Some of the AR style stocks are good and some are definitely not. Unless you need it to adjust for big/little people, I would just look at a short LOP. At least until/if someone comes out with a stock to fit.
I might tend to think conventional powder coating may not work on plastic, but again, someone who has been there and done that will know more.
Welcome to the Basement by the way.....