Uh, OK. So what is the metaphor of the sphere and what does it mean in relation to the body? I have never heard of this metaphor and have no idea what it refers to, and I'm probably not the only one. I have no way of knowing that there is a metaphor relating the body to a sphere unless someone says so...
My point in responding to the question about the sphere with a comment about different models of the sphere is that -- it depends what you mean by a sphere and it depends what you mean by stability. I.e., more info is needed to answer the question of whether a sphere is stable.
Personally I usually find mechanical models clear and metaphors just confusing unless I already know what the metaphor is talking about. So I often have no clue what people are talking about until they stop using metaphors and tell me directly what they mean. I have met people who were the opposite.
Well that's a personal choice I guess.
The Asians I have met who had unusual power- all use metaphor.
The Tom, Dick and Harry Western guys uses mechanical models.
NONE of the Western teachers I had personally met
feel any different than every other Tom, Dick and Harry. I'll change my mind when I find someone who uses the mechanical models and actually has something unusual to share. So far its been a bust.
Six direction method imparts a sphere -in theory- but it uses the mind/ body in specific ways to manifest that feel. Think of one point as a model. There is no sphere, so talking about how strong a sphere is and the qualities of it are waste of time. You cannot make a sphere out of your body and if you try, you will fail in innumerable ways. Likewise there are innumerable Aikido people who claim to use Tohei's model or to understand ki who have nothing unusual by way of power. Their one point is sort of okay under dojo conditions but fails under stress. Using the sphere as a mechanical model is inefficient. Describing what the body must do to manifest six directions is an exacting model that is a success. A success with a history.
Remember, Ueshiba was talking about the body...and not the "spiritual" things people erroneously assigned to his physical principles.
The really wonderful question is why does six direction blow up the push/pull model? The answer is simple but very hard to grok at first, harder still to do. Most simply cannot see how you could be in agreement with someone and totally neutralizing them at the same time. Moreover what that does to your own body to strengthen it and how? And if you understand THAT then you understand that making aiki between you and them like the oft quoted four legged animal between you and someone else was flawed from the start. Takeda, Sagawa, Ueshiba, Shirata had it right.
There is no debate in person. So I prefer to debate in that venue, where teachers have to provide proof of their understanding in an inescapable venue under stress.