Sitting back is invariably superior, even with narrow stance squats, front squats or other "knee break" (as opposed to "hip break", in terms of where you move first). Here is a quick overview of how to wide, or semi-wide stance (athletic type) squat, using the sitting back style:
1. Set-Up, get the bar in the right place on your back. Some people go lower than others, but nobody is better off with a highbar for powersquats. Squeeze your shoulder blades together, and make sure your upper back is nice and tight, and your lower back is in a hard static arch before you unrack the bar. If you're walking squats out (which you probably are) really work on getting the walk-out short and effecient. Don't spend a bunch of time dancing with the weight. Take a big belly full of ear and press your abs agaisnt your belt (if you're wearing one) or distend your 'belly" regardless.
2. Descent. the first movement of the squat should be the hips/butt going backwards. Keep the head slightly elevated, chin up, chest out, back arched and push that butt out J-Lo style. Eventually you will reach a point where you feel like you have to "gm" to make depth, instead push your knees outwards, or "open up the groin" as Ed Coan said. You lean almost between your legs (and literally so if you are long of torso, big of belly, or both like me).
3. Out of the Hole, once you have gone below parallel, it's time for the hard part; getting back up. The first thing I will say is key, because so many people do it wrong. The first thing you do, when you're ready to come out of the hole, is push your head and shoulders up AND back against the bar. Think almost of trying to throw the bar off yoru shoulders. Then shove your hips forward, and push with your heels. It is key that you keep yoru back arched, and your head up.
It could also be a muscle imbalance. Lets start with the easy shit first. Increased core strength is always gonna help a lifter stay upright on the squat. Hit up some heavy sidebends and weighted sit-ups of various types. Also, if you feel experimental, try unracking and walking out weights in excess of your 1rm and standing for a count of 5-10 seconds.
Now the harder part. Targeting muscle weaknesses ass you advance can be difficult, because sticking points may manifest in a place that suggest weakness of another area. Take the bench for example, you can have trouble locking out (normally indicating a tricep weakness) caused my a weak chest, and not getting enough speed off the chest. So my guess would be it's actually your hips/glutes that are potentially weak, if it's not a form issue. Solution? RDL's and/or Wide Stance GM's.
