Re: Where's the hara?
"hara" only overlaps with the "center of gravity" in terms of meaning here and there. So, in my opinion, it doesn't serve one too well to only think of the hara as the center of gravity. There are many more connotations associated with the hara that are not associated with the center of gravity. Also, the center of gravity is not a specific location in the body. It is dynamic by nature and is in a constant state of flux. This is because movement, which effects the positioning and balance of the body, is always in a constant state of flux.
When I first trained, I was always told things like "move from your center," "use your center," "concentrate on your center," etc. As a teacher, I realize that if you don't have your center already, these phrases are basically meaningless since there is no common point of reference being used - no shared context. I have only found them to be useful in terms of getting a student to grasp the concept that there is more to know and do than they already know and can do. For me, phrases like these have only become truly efficient when I combine them with some basic exercises which work to establish a common reference and/or context regarding "center."
For example, it is important to realize that the center of anything can only exist because there are at least two peripheries. It is also mandatory that these peripheries are in a relationship to each other - a co-dependent one. Thus, if you want to find your center, particularly before you know what that is and/or before you experience what that is, seek to establish a co-dependent relationship between the two peripheries which are the very things that mark and define "center". In particular, and most commonly, be sure that your head and feet are in a constant and co-dependent relationship to each other. When they are, you will have established centered movement. When they are not, you will have lost center. This is why awareness must not only go to some point abstractly located proximate to your navel - awareness must travel the length of one's body - from head to two - then center will be manifested naturally, almost of its own accord.