The original posting:
… The pelvis and its tilt is involved. Demos can be a bit... shall we say... interesting.
The other is how significant the disadvantages of the arched back are, since the decision to talk about it rides on that significance.
The impression I have is that an over-arched back is a significant disadvantage, though a mild arch is part of a proper basic stance, because too much arch usually has the skier bending forward at the waist in a crouching position that makes the quads and back muscles work more than they would if the stance were more upright. You are not well “Stacked”, skeletally, if your back is arched too much. (For those whose minds are in the gutter, you are invited to refrain from alternate discussions of ‘stacked’.)
The original posting:
If you are not an instructor and you've had this discussed in a lesson, how did that go over?
As an occasional member of group lessons I can report that the subject usually goes over well, even with mixed gender and mixed age groups, because everyone has some level of interest! From a few of the less prurient instructors I recall at least two fairly benign descriptions and analogies to make the point. One “clean” set of cue words I have heard is based on demos of how to Close the Drawer, as in, Imagine you are in the kitchen cooking or baking and both hands are covered with whatever you are working on, and you need to close a drawer but do not want to get the mess on the drawer. The drawer is about hip-high, so give it a push with the tip of a hip bone to close it.
The ‘push the drawer with a hip’ is also one way to think of what you do with your hips when moving forward and laterally across your skis to initiate the kind of garden variety extension-based turn that is taught to advanced beginners and low intermediates. I have also heard it described as leading with the inside hip, or leading with a strong inside half (which makes me wonder what a weak inside half would be).
Some instructors use the cue words Stand Tall after demoing what the skeleton should look like when Standing Tall. Standing tall rotates the pelvis to the front and reduces the excessive back arch that is seen in so many less-than-confident skiers.
That is one view from one member of the lesson-consuming public.