I think I understand you to be expressing a sense of mushin awareness.
Minenori and the monk Takuan spoke of this as "moon over the water" and other very vidid images.
What I take that to mean is that one is aware of all things yet not fixed on any one thing.
I laud you for being able to reflect upon they various principles you remember employing. The moon was well reflected in the water.
What memory did you have about and within your body, your spine, your hips, ankles and shoulders, your belly?
Thanks for your response. Your questions are interesting and unexpected. Memory of certain parts of body? None. That's the simple answer. Not memories. I am only aware of the principles and resultant feelings from such areas but more as standard procedure. Thus I can relate what happens in those areas you describe, for me anyway, but at the time of doing they don't take any attention if you see what I mean.
Your statement of taking it to mean one is aware of all things yet not fixed on one thing I find interesting too for I find the opposite is true actually. By focusing on one thing, in the example I gave of sword, then note the one thing was center line. By so doing you become aware of everything. This is the whole theory realy of one point as given by Tohei or as used by Mas Oyama which he took from kempo ie: the principle of keeping one point and the resultant relationship you come to realize about the circle.
However, I would simply put it this way. All meditations are based on this principle. Whether they get you to listen to the sound of water, concentrate on a box or some image, whatever. They are getting you to concentrate on one
'point. This leads to becoming aware of all around.
This is another principle to be understood and applied. Another example would be someone flashing a knife in front of you, slashing from side to side etc. The motion takes your mind. You get involved in the 'everything' of the motion so become aware of nothing, lost. On the other hand if you focused only on center line it would look to you like a pendulum swinging. You will see everything and all the openings and even as if you are watching in slow motion for yourself. This is also what I find to be true.
So the truth to me is: Try to focus on everything and you will see nothing, you will be lost. Focus on one thing and you will see everything.
As far as the body parts go I can only explain this way. The stomach? I feel only center and one point and thus the energies of hara and the inflow and outflow through such. Thus the stomach fels like a gateway of yin and yang I suppose you could call it.
The spine feels only like center line feels, a neutral axis around which all turns. Also it feels like a neutral passageway for Ki between heaven and earth so to speak.
Shoulders feel invisible, gone, is the best way to describe that.
Hips feel like the opening which allows all counter energy to go to earth, not necessarily through the legs. I call this Koshi, the base of the spine area. It connects with mother nature and the void both. This is how I explain it.
Ankles seem to have no relevance feeling wise. The legs and feet once again feel hollow yet full of energy going through to earth aligned with koshi. In motion they are just part of the motion, I am oblivious to them.
As an aside I could say via the legs for example that wasn't obviously always the case. Positioning and direction of feet and knees etc. and relationships to motion and direction and even direction of cut of the sword all had to be drilled in and would take attention of course whilst learning.
So I hope that gives you how I feel and experience with regards to what you asked.