For awhile I have been struggling with the meaning of the "Eight Powers" and how they relate to our training. I'm reminded by your article that he expressed them in terms of pairs of numbers (9-1, 8-2, 7-3, 6-4 etc), stating the different relationships between yin and yang, but it seems in Aikido that we aspire to do just 5-5 (circular aiki?). Do you think the more (uh, linear?) aiki was taught/demonstrated by O-sensei? Or perhaps it's one of the differences between his pre-war and post-war art?
I don't think that conventional Aikido (modern Aikido?) pays much attention to it, although they certainly ought to, IMO.
The eight powers are different combinations of yin and yang that produce different effects or "jins", basically speaking. In terms of the balancing, as we see in Morihei Ueshiba's citation of Kiichi Hogen
, the actual numbers don't matter so much as the fact that they have to balance. Without that you can't get the neutral, and you introduce stagnancy.
Of course, it's important to remember that there's something missing when Morihei Ueshiba talks about yin and yang, and that's...the other person. He references it (as you know) in terms of oneself, in terms of balancing those forces within one's own body - "I am the Universe", not "You and I are the Universe".