If you plan on running 12g, I wouldn't buy the SS-25 to do it with. It more of a DF with HPA pump. Or even SC feed with HPA. I'd guess you'd be lucky to get 20-25 shots of a 12g with them. Unless you did some serious tweaking.
Live or play near Metro STL? Organizing monthly pump meetups at the many different fields near STL. Check out "STL Pump Group" on Facebook for more info. Best Field in STL