Re: Moving with your center
I think that for so many who practice aikido, discussions of "extension of energy" and the like are like critiques of the emperor's new clothes. That is to say, you're trying to understand the nuances of something that may be a metaphor, may be a colorful way of describing a series of mechanical actions, may be literal truth...could be all of the above. Maybe. I don't think it helps, though, to get engaged in a discussion of whether the emperor should be wearing that shade of blue, when you're not really sure if he's even wearing clothes. If you're not seeing the clothes (either because you're not able to yet, or because the clothes aren't even there, doesn't matter which), then don't get involved in a fashion discussion, that's my advice. Don't get involved in a fashion discussion, and also, don't waste your time trying really really hard to see the clothes. If they're there, they will become apparent in due course.
Meanwhile, practice. Don't worry if you don't have the grand unified theory of energy extension. You know enough by now to do good practice, so concentrate on what you do know. Focus on basic mechanics: "energy extension" can't make up for a sloppy stance, badly distributed weight, hands held carelessly, pivoting on the heels, etc. It's my personal belief that good basic mechanics are a prerequisite to anything like "energy extension": you can't go off into a room somewhere and gaze at your navel until you have an "energy extension" breakthrough, and then bazing, all your mechanics are superb. Rather, having bad mechanics is a perennial obstruction to any breakthroughs at a higher level, and having good mechanics clears the way so that such breakthroughs can happen. They don't guarantee that it will happen, mind you -- that's where patience comes in. Focus on doing the things right that you know how to do right, be patient and content with striving for that, and let breakthroughs happen in their own good time. Personally, I've never experienced or noticed a martial arts breakthrough in the moment, as it were. It's always a case that I suddenly notice something that's been there for a while...never a case that I do something right for the first time and say, "Aha!"