Well, they're sanforized, so you shouldn't get much shrinkage at all; maybe .5" or so is about the standard. To cut down on the stretching in the waist, you should wear a belt. Even if they aren't tight, they'll stretch some in the waist simply from movement. No way around that, really. I'm not intimately familiar with the SBG denim, so I can't give you any more specific info, sorry.
well thats a good start anyway! thanks man.
I may end up just ordering the size down and just comparing when i have both in my hands.