A number of people have stated that raising the toe piece (decreasing the net ramp angle of ski, boot, and binding combined) will move the hips forward. Others have stated the opposite. I'm not convinced that there is a solid correlation for a general population. A long time ago I helped my kids with a science experiment. We tested 4 of us (mom, dad, son, daughter) by first increasing the toe height and then the heel height with the tip and tail of the skis on two different scales. We each tried to establish a comfortable, natural skiing stance for each measurement and averaged the results over a number of trials. For 2 of us raising the heel piece moved the center of mass (as measured by the relative weights shown on the scales) forward and for 2 of us it moved it back.
This simple experiment is certainly flawed in that a static stance on flat ground does not simulate the dynamics of skiing. However, it is enough evidence for me to question a hard relation between ramp angle and the positioning of the center of mass. The underlying assumption is that there is varying response among individuals to a change in ramp angle.
I would love it of someone with video and willing subjects would film a group of subjects skiing the same slope with their regular setup, raised toe, and then raised heel. I think an experiment like this would be very helpful in illuminating whether there is or is not a solid relationship between ramp angle and fore/aft positioning. Of course, the more subjects filmed the better.