To find your ideal stance, get on a slick surface like tile in your socks and get into your normal snowboard stance. Now, squat down and go as low as you can comfortably go. Raise up and squat a few times to find your maximum range of movement. As you squat, your feet will slide out to their ideal width and you will also notice that they will angle out to where they want to be for this. Have a friend or significant other, measure the width (center of foot to center of foot) and then use a straight edge along your heels and measure the angles that your feet have assumed. Match these measurements on your board and go ride. Most people find the best performance overall and most comfort after setting their board up this way.
I've done that before. The funny thing is, I ended up pretty much at the 68cm I'm using. I may be weird, but squatting/getting very low that way is a lot more comfortable for me. With the wide stance, I'm utilizing more muscles and it's less strenuous.
Thinking about it, I was doing fencing in a previous life - that may well be the reason I'm so comfortable with the wide stance.
I was wrong about the angulation thing, I mentioned in the first post. There is no difference.
As for some of the issues you describe, even with a narrower stance, you can use good independent flexion and extension as well as overall lower riding posture to absorb vibration and chatter from shitty snow conditions.
Sure, I do that. But that only works to a certain point, if the speed/chop frequency gets too high, things are far better with the wider stance; the board cuts better through the chop, it has less leverage against my legs and I have a lot more strength.
Doing some squatting exercises, the strength difference is surprisingly large - that may actually be the biggest factor (in that I can leave my legs 'looser').
Too wide of a stance can be just as limiting to this as too narrow. Additionally, fore-aft movements timed right can help quiet the ride. Again, too wide a stance will limit your ability to do fore-aft movements as well.
My fore-aft movements work better with the wide stance. I have no problem getting completely on my front or back leg (beyond a 90 deg angle board/leg). With a 68cm stance vs. a 60cm stance, I'm getting close to 8cm more weight shifting range.
It should not be necessary to bow your knees out to "derocker" the board to increase turn radius. Simply toning down the tilting movements can accomplish a lot of this.
Yeah, doing my carving experiments, I think I was using a lot of that to cover sloppy technique. At the same time, the board is rather stiff, I'm a little below the minimum weight listed for the board and once it's on edge, it turns extremely fast. (The board has really been exposing a lot of sloppy stuff, I was doing.)
When I was turning the hips, I probably rockered the board even more.
With the wide stance, I can perform smoother edge switches and set the new edge better (when I don't rotate the hips). So I don't need to de-rocker the board, if I watch my hips.
Even so, there can be times when this movement has value in your carve and I would again say that if you find that you can not do this, it is a clear indication that you have indeed too wide of a stance.
It was turning the hips that screwed me up here. If I keep them in line with the board, I have no problems going beyond a 90deg angle between lower legs and board. If I don't turn my hips too much, I can get the board flat with the wide stance (ok, with the narrower stance, I can 'camber' the board).
Anyway, even if it may not sound like it, I do appreciate your feedback. Even if I don't go to narrower stance (it looks like, I can make things work quite well; I had some runs with really clean pencil-tracks), it's helpful to think about what I may or may not be be giving up and where I may encounter bio-mechanical limitations.