An S-Trim I'm pretty sure the S-Trim has a max of around 20 pounds, however at that point you'll need the intercooler and probably internal engine mods. Without those two itimes the S-Trim can go safely to around 10-12 lbs. Take a peek at the two web pages below for more details.
http://www.motorsportsdigest.com/forced-vor.htm
http://www.vortechsuperchargers.com/