OK, was playing around with "separation" (or was it "counter", the terms confuse me at times!) the other night...
Anyway... here is the exaggerated version:
1. Travelling in a straight line on a reasonably flat surface.
2. Stand up out of the saddle.
3. Tilt/tip/angulate/... the bike over to the left - the bike will start to turn.
4. Tilt/tip/angulate/... your upper body to the right so that the bike goes straight again.
Then I tried it by tipping the bike to the left, and just shifting my hips to the right.
Then I also tried it while seated.
Now, I've no idea if this has a practical application in skiing, because I was only able to "control" a straight line. Controlling a turn took a lot of work, so it did not seem a valid way of enjoying riding. (no, I didn't fall off)
Also, the "separation" was more in terms of Bike/body rather than Lower/Upper body.
I'm selling the bike next week when I leave France, and then I'll be back to trying these experiments on a good racer rather than a cheap mountain bike.