I dont' think a Supra SMIC will work with a 20g, period. Its not all that much better than the stocker. Granted, it is better, but not NEARLY as good as a FMIC. It'll work for a Big 28, but why not just go FMIC? I kinda feel like the supra side mount is a temporary solution to a bigger issue, and is alot of money for a at that. You're gonna eventually want the Front mount anyways, why spend 200 on another side mount?

You can also keep boost down on the stock side mount w/a t-28 until you get an FMIC.

Plus, big 28 is apparently a breeze to install, and you DO NEED an install kit for a 20g, just like you would with a 16g... :thumbsup

Vandy