If anyone has worked on creating the disc, you may have noticed a few things. The disc itself is right at the same height as the head (ball) of the femurs - within the overall area known as the hips. It's not at the waste. Yes, there's a term for it within CMA, but I'm not interested in using foreign language here.
Simple, effective, and powerful tools that yield demonstrable results on which to build.
Here's an email that was sent by someone who's been working on this:
Last night was my first class since we discussed the disk. I have been working a lot at home with your concept and had a very different experience at class. From the outside it may not have looked any different, but internally it was very different. First, I could articulate what I was feeling in a way I havent before. I could sense my energy rising, in a bad way, when I was losing balance. This gave me something to focus on in (keeping the energy low). Additionally, I was able to be much more effective moving uke's center. I knew this based upon the comments (and falls) of my partner. I was surprised as the feeling of doing it right (or more correct) was not what I expected - much more subtle. Lastly, my balance is improving. So yes, I definitely want to work on technique stuff.