I'm pretty sure I started a thread on it when I first saw the stemstep. Let's see if I can find it....
Here it is - http://forums.epicski.com/showthread.php?t=33276
- look especially at posts #33 and #36.
So stemstep synopsis (I understand this a lot better now than when I first posted on the subject and actually teach this thing sometimes).
The stem step is a turn where the new outside ski moves up the hill at transition. The center of mass is moving downhill while the new outside ski is moving up the hill.
To some degree, this sounds (and looks) like the White Pass turn. What's different is that the new inside leg is flexed at transition and you are extending the outside leg up to the stem. In White Pass you have two long legs at transition and softne the inside leg to bring the outside ski into contact with snow at the fallline.
When the examiners demoed this in my exam, I saw it two ways. One examiner was standing on both inside edges during the maneuver, and te other two showed a simultaneous edge change. Either way was fine as long as you moved the CM inside the turn.
The bottomline on this maneuver (and really just about anything you do in the exam) isn't the maneuver itself, but the movements you use to execute it. If you are skiing well, this maneuver should feel easy, just like god skiing. If it feels really awkward, you need to break down the movements in your skiing and see what's making it hard.
p.s. - I'm in Eastern Division, not Central. You could see anything at your exam.