Mike I've noticed the width of your stance change throughtout the years. Ive added alot of stretching my program and can now hit depth with my feet against the rack. I've noticed a huge improvement in the strength at the bottom of my lift when I do these wide squats, but Iv'e kept it pretty light (around 300). I've yet to try this technique with a heavy 400+squat but am curious, any argument either way? Why have you moved yours around?
I used to squat very wide (feet to the sides of the rack), but I had trouble consistently hitting depth at that width. That was one of the results to come out of 2006 collegiate nationals. I was tired of only getting 1 squat in at the meets.
So I closed my stance some. I work it around a little now, because as my strengths change, so does my form and technique. Also, it's in part due to my own human inconsistencies. If you go to the sides of the rack, you always know how wide to put your feet. Anything less than that, you're sure to get slight variances. That being said, we do try to avoid them as much as possible.
Also it bears mentioning, I don't try to change it very much anymore. The tweaks I make have more to do with toe positioning and set-up that the width of my squatting.
I guess I should also mention that I think the best stance is the one where you are the most bio-mechanically sound.
Look at Andrey Beleyev squat, then tell me he'd be better with a wide stance. Bull. He is 100% biomechanically efficient where he is right now. Same with all the legendary guys like Coan, Mike Bridges, Brent Mikesell, and so on. I've seen those guys (except for Coan) squat in person and it is ABSOLUTELY poetry in motion. That's what you want to achieve.
How do you do that? Well, that's more difficult. I look at bottom position. Have someone take a picture of you in the bottom position of your squat. Here's some things you want: Standard "good technique" (back arched, chest up, legal depth, etc) barbell, knee, and ankle in the same vertical plane shin bone vertical both when viewed from the side AND WHEN VIEWED FROM THE FRONT Foot and femur flow in the same line pointing back to the hip joint
And I'm sure there's more, but that's all I can think of right now. I hope that helps.