First I'd like to introduce you to my good friend Tony. He actually spells his name ToeKnee. He's actually a very smart guy, but his spelling is awful. You could say "Tony knows how to ski", but he would write "ToeKnee Nose how to ski". The moral of the story here is that having your toes, knees and nose in vertical alignment is a good thing for skiing. But this is a reference, or average alignment position. During skiing, we don't just hold one fore/aft position. We move back and forth a little during a turn. The key factor is that we need to be moving forward as we start a turn. The problem with your reference position is not your shoulders. It's your belly button. Expose it to the wind more. If you do this, you'll be in a better position to move forward at the beginning of the turn.
With respect to extension, you can think of it as reducing extension of the new inside leg. How I think of it though is the opposite of extension. Instead of getting both legs longer to start your turn, I want you to keep getting your new outside leg longer, but start making your inside leg shorter (instead of making it less longer). To see what I'm talking about here, try the indoor drill I was talking about (oh rats - that's a different thread
). What you'll find most helpful is another variation of this drill. Instead of moving the hips forward, start with a movement that just lifts the outside ankle up (stand on your toes only on your outside foot). This will cause you tilt laterally. Now try just bending the new inside knee. This causes you to rotate your inside hips and shoulders forward. Now do both movements together. The hips and shoulder stay level but move forward into the new turn. When you do this right, you'll need to catch yourself against the wall. When you do this on snow, your skis will catch you as they accelerate into the new turn. When you don't do this on snow, your skis will get ahead of you.
Angulation refers to when the line from between your feet to your belt buckle points in a different direction than a line from your belt buckle to your chin. What I'm referring to is called counter. This is when your feet are pointing in a direction different from where your shoulders and hips are facing. We look for separation between the upper and lower body in 2 different ways when we ski. Angulation is when we tilt at the hips to get the upper body to be vertical over the snow when our legs are at an angle. Counter is when we twist at the hips to get the lower body traveling in a different direction than the upper body. Together, the two of these things allow us to stay in balance while the skis do their thing. I want you to use more counter (i.e. get more difference in the direction your feet point versus the direction your shoulders point before you start your next turn) in your skiing.