I hope I'm close on this, but the keeping the midsection tight really benefits a lot. There's two ways that I read you can do, one is preferred over the other. The first one is to suck in the gut and hold/flex in tight, like if you were doing a crunch. The other is to fill up with air and flex as well. I read (sorry no link to back this up) that sucking in the gut while tightening is most perferred and better. I have problems with my squat too, so I lighten to load by a lot while practicing this technique, and didn't seem half bad.