In order to not only change your stance, but to introduce the movements that go along with skiing a more "modern" stance I think I'd back up a step and take it back to basics. I've found that a really good drill to promote both a good athletic stance, as well as increased angulation while maintaining that stance is the following:
Start on one side of medium to wide trail, flat to mild pitch. With skis pointed across the hill, try and obtain a good athletic stance, feet shoulder width apart, hands up, body centered, knees bent (may require an instructor to demo
). Next practice rolling both knees simultaneously into the hill. You'll notice this is increasing your edge angle on the snow. Try and do this simply by rolling the knees (ie. without leaning too much), keeping your shins parallel. Now this is where the fun starts..
Next what you're going to try and do is point your skis a little into the fall line. If straight down was 90º to where you were, than lets say 45º. As you start to slide across the hill, while maintaining your athletic stance, we want to lean slightly into the hill to get a slight bit of inclination happening, setting our edges. Then gradually roll your knees into the hill as you did previously, wile stationary. You'll notice your skis are going to be carving, and taking you in an arc up the hill. When you get to the other side, look behind you to see if there are two clean "rails" in the snow. Try again to the other side. Continue to do this a few times until you've adjusted to the new stance and the new feeling of having both skis carving.
Now try doing two turns together. Release the first turn in the same manner you built it. Roll off your edges first with your knees to re-center and flatten the ski, initiate the new turn, and do the same process described above as you go across the hill the other way. As you start to catch on to the carving feeling, you'll notice how both of your skis will begin to work across the fall line, and how your wider stance will make you feel more solid and confident.
To take it to the next level, as you go through the release process, rolling off your edges try rolling onto your new edges for the next turn before you turn through the fall line. The only difference between what you practiced above and a fully linked carved turn is how soon in each turn do you roll onto the edge and start the ski carving.
This is a really great drill, and I've used it a lot, and seen it do wonders. I just wish I could give you a demo! Hope you're able to understand the concept. Just take it back to basics.