Re: Where's the hara?
I agree with what David Valadez has said here (and on his web site by the way).
To expand on that a bit, I'd say that when students have no common point of reference, it is much better to talk about maintaining your posture and moving from where your legs attach to the trunk of your body (as the center of your movement). That will help people ensure that their "head and feet are in a constant and co-dependent relationship to each other," resulting in somewhat centered movement.
Several really good sempai have explained to me that "hara is emptiness" and that has been making more and more sense to me lately (in terms of feeling). It helps me work on keeping things intimate and not personal.