Hmm... already tried this without success. Something I'm doing wrong for the pix.
Anyhow, there is the proper direction (as seen parallel to the mats) for kuzushi, then there's the proper 3D direction.
I was taught it is generally about double the upper arm length of uke's upper arm - so seen from overhead, the correct distance is around that of uke's forearm, with a perpendicular drop down. Judo Vitruvian Man - Overhead
Seen from the side, it looks somewhat like this:Judo Vitruvian Man
With appropriate apologies to Leonardo - he was simply looking at proportions, I'm looking at equilibrium, kuzushi.
Comments welcome - this is a work in progress.
I am puzzled by this. So, I should reserve any judgment until I understand the rationale of what it is you are doing/proposing better.
Kuzushi is something that can be approached from a historical point of view, a philosophical point of view, and a scientific point of view. One should realize at all times that these are three different approaches. My initial worry is that you are conflating these boundaries. Referring to someone as Arima is fine as long as one's approach is historical, but not from a scientific point of view. Scientifically there are many flaws in Kanô's approach due to him apparently having no knowledge of the serious physics and biomechanics work of people such as Bernouilli. What Kanô did was provide a PEDAGOGICAL system and the contents and objective of that system was to FACILITATE learning, but the pedagogical approach is often at odds with the science. For example, the entire categorization into te-waza, koshi-waza, ashi-waza, etc., is scientifically nonsense, but pedagogically helps the learning experience and a certain categorization of jûdô techniques. It's a bit like trying to feed a toddler a sandwich. Mom may take little pieces of bread and tell the toddler that they are birds or planes and he needs to catch them with his mouth. This may actually cause the toddler to eat, so it is effect. Clearly, if we would attempt to use a scientific approach and analyze the flight characteristics of the sandwich, it would make little sense, since what took place was merely metaphoric, and we made use of that metaphore to construct a pedagogy.
About 1.5 years ago I wrote a long paper on kuzushi, but I never published it or submitted it because it started off from Hirano Tokio's conceptual approach, and before I could publish it I was approach to author a book on Hirano, so it would make more sense to integrate that part into the book. Anyhow, it deals with some of these parts including the pedagogy, history and science, but not the Vitruvian man, as I fail to see its relevance. However, if your intent is pedagogical, clearly everyone can make whatever pedagogy of jûdô. The only criteria to evaluate a jûdô pedagogy is if it facilitates the learning. But ... as described above, this is something entirely different from the contents of that pedagogy being true at all.
Understanding kuzushi, scientifically, is a mere matter of Newtonian mechanics. The philosophy and pedagogy are entirely different. No matter what budô system, the Newtonian mechanics remain unaltered, but any style may and likely has its specific philosophy and pedagogy.
What I see in the model you propose, I cannot immediately link to any of these, but if it is a personal pedagogical model you propose, then this is also logical because then it is new and I first need to listen to you to better grasp what it is you propose and how that is aiming at facilitating the learning. I cannot place what it is you describe --in as far as I understand it-- within my technical, historical and scientific knowledge of jûdô.
IF one wants to propose either a new pedagogical model or IF one wants to go back in time to provide a historic overview of kuzushi, my suggestion would be to make it easy for yourself (the word 'easy' here is very ambiguous as you will soon see) and make use of the work that a number of serious judo biomechanists have done before you, notably the work of professor Sacripanti from Italy, professor Trilles from France, and professor Yabu from Japan. Unfortunately, the work isn't easy in itself (hence the ambiguity I was referring to). Why reinventing the wheel ? If on the other hand your objective is to propose your own jûdô kuzushi pedagogy, you cannot afford in 2014 what Kanô could afford himself in 1882. Kanô could then get away with not properly knowing Bernouilli; you can't and will have to incorporate today's knowledge. The scrutiny does not come only from the scholarly work, but also from the practical world, as demonstrated by some of the not so successful jûdôka's experiences in MMA. I mean ... anything new, technically new, you proposed won't be accepted with quiet respect as in the days of Kanô and in the Japanese society, but will be met by skeptics promptly wanting to test out the credibility of such a approach in noncollaborative practice.
That being said, there is also something of important merit in what you write, but I am not sure that it is sufficiently clear for most readers as described in your post. So, permit me to paraphrase some of this. Kanô's model of kuzushi, i.e. happô-no-kuzushi is a 2-dimensional model. It basically talks about horizontal directions, wind directions if one wants, 8 of them. In reality, kuzushi is, however, not 2-dimensional, but 3-dimensional meaning that in addition to the wind direction, for example East, the kuzushi could be slightly up, slightly down, very much up, very much down, not up or down at all. It is a great weakness of Kanô's pedagogy that he failed to incorporate this in his pedagogy, and it is partly responsible for why virtually everyone in jûdô struggles most of his life with proper kuzushi. Because Kanô never provided a 3 dimensional model, the consequence is that the 3rd dimension is now incorporated only when you learn a specific technique, with that 3rd dimension being different for most throws. Kanô has not addressed this problem. One could claim that he deliberately did not include a third dimension, but I do not believe this to be true. Given Kanô's prevalent weaknesses in physics it is rather logical he failed to realize it, or at least failed to realize it in time. Whilst the structure and pedagogy of tachi-waza in Kôdôkan jûdô is much better developed than that of newaza, the issue pointed out above remains one of its biggest flaws even in the light of Kanô's strength, i.e. pedagogy.
When I wrote the paper I referred to above, I tried to address this because one of the major merits --and this without the world actually realizing this-- is that Hirano Tokio did actually in his pedagogical work include such a third dimension. However, failing to have the support of the Kôdôkan, but also because no one really realized the existing problem in jûdô and Hirano's solution, his major contribution to this day remains unappreciated. At the most people recognized the beauty and skill of his jûdô but not his specific pedagogical merit.