I have uploaded a new version of the Mentoring/Training scenarios which include the hidden units rules. Those of you in the first half of self-study should download it.
It has always bothered me that the optional rules were never published, only posted once at APL and are difficult to locate. Since hidden units is a frequently called upon rule in scenarios, and is in the third Mentoring scenario. That was the reason of the revision. A little off cycle, but not disruptive.
... More and more, people around the world are coming to realize that the world is flat!