I've been thinking on these discussions all day and would like to muddy the waters a bit.
First it is very difficult to follow the shorthand descriptions given for power generation, whether Chinkuchi, Sanchin Points or Nihanchi Points or others. This is natural because the technical vocabulary to really transmit this material doesn't readily exist. Individuals are taught in person, not by written word and without taking the time to share in person it's questionable whether we can really realistically understand even the surface of these conversations.
This is compounded by the fact that the verbal shorthand we use really never actually describes the full motion involved. Whether discussing the stance, the method of movement, the area of the body involved (hips, Koyshi), alignment, etc. all those answers fall short. They're way to try and grasp a larger issue, that of what is actually happening, and focusing on a single area to try and use that focus to improve. In reality many of the different concepts people are vigrously discussing exist in each others grounds of argument.
For example I don't accept it at all that one can only follow one way or another and that's multiple ways just get in the way of each other. But then its a question of personal experience. I've trained with many artists who follow multiple paths successfully. That's not saying its easy, in truth it takes a full time committment and good instruction, but it is possible if one really wants to pay the price.
Now that may not be 'good' politically correct Isshinryu (or many other arts) but it can be done and is done by some. What is difficult is to do so with less than a total committed effort and great instructors.
Now when the debates get to power generation I've been trying to follow that from my own beginning studies.
First we should consider that power generation is only one, and perhaps even a minor aspect of what it takes to sell a technique. For with power comes tactical effort, too. A less powerful strike delivered at the correct tactical point and time can accomplish as much as a more powerful strike at a less opportune moment. But tactical study is often very short changed.
Power is also not just a component of how you generate it, when you have two bodies rushing at each other and you work on your kata applications you can disover some of them take the shortening distance between attacker and defender into account and sell themselves in those ranges, so fast the defender doesn't realize they've wiped the floor with the attacker. Unfortunately for my students we've often discovered this when I've had another bright idea and tried to learn a new application potential at slow speed and end up picking the pieces up. In such cases the kata itself may be the answer.
I'm not against power generation study but I've seen many answer that all seem reasonable. Perhaps its the faith of the practitioner in their way that is the key. If they work and really believe it they'll sell it, if all the components are equal.
Among choices of power generation are:
1. Refinement of original basic kata instruction, developing cleaner technique execution, combined with correct tactical usage.
2. Tournament karate. Alas for its detractors I've seen many whose skills could transfer with correct tactical usage into solid defense.
3. Chinkuchi. Now one of my instructors, Charles Murray, trained with Shimabuku Sensei and Shinso a bit a while ago. You may have seen the notes he made when he returned to the states in the early 70's. One of the last things he shared with me before returning to the USAF was how he was trained in Chinkuchi, and over the years he's shown me his continuing efforts on those studies. But seeing and being trained are two different things. I didn't have the chance to pursue the training with him and had absolutely no interesting in trying to work it out on my own... But I've felt what he does with those strikes.
3. Usage of Sanchin. Perhaps in part focusing on the linear power release. I agree Sanchin is increcibly valubable and can tactially be used to demolish any sort of attack. I'm learning to realize how it can be felt throughout the Isshinryu system a little.
4. Usage of Nihanchi. perhaps in part focusing on the circular power release. Ditto. The source for so much power, the key to Chinto for example, but if one just did Chinto correctly the same power would be being taped. Where one choice is to focus on a fundamental concept and then keep the focus there, there is just as much logic in focusing on other kata similarity.
5. Knowledge of fractal movement application. This is where sub components of our movement become weapons in their own right, and their usage is different from the large technique they come from. There are tools that help unlock their usage, such as the knee release to change the angle of application instantly.
6. One of my instructors at 3rd dan in his combined Shotokan/Tjimande and Aikido training literally changes the nature of their art's execution to dramatically increase the reaction speed of the dan. This becomes a more intersting component of power. If your movement generates more power but his nails you first, fastest, which is the most important. Never a simple answer.
7. Bushi No Te Isshinryu. Over the years I've developed my own signature use of the body incorporating driving all technique power off of the centerline incorporating knowledge of body energy point alignment and even the manner of breath execution in technique. The words don't do what I mean justice. But in my students own manner we work at trying to ring the maximum return from our technique. I make no claim what I teach is right, it's just what I do and I'm satisfied with my students return on the effort.
8. Yang Tai Chi Chaun. Develops power with a rolling center and correct energy point alignment in the flow of technique.
9. Wu Tai Chi Chaun. A different, more subtle energy flow and release from the Yang, in my initial studies to date.
10. Countless other exist too.
It seems rather pointless to pound one's chest. If you have a path that works, fine for you. If not work harder.
These concepts are not words. They're Isshinryu of Tom Lewis, Reese Rigby and Charles Murray, The Kung Fu and Tai Chi Chaun of Ernest Rothrock, the Shotokan, Tjimande and Aikido of Tris Sutrisno, and the sweat my own students have offered too.
The interesting thing is they all intermingle too.
The energy I observe in Chinkuchi is suspicously similar to the release of Hsing I, a Chinese system IMO.
The energy in Nihanchi is found througout Chinese systems.
The alignment theories (of various types including bows and energy points which both seem to describe similar things from different points of view) exist in all arts when a technique is correctly done. This just explains why they work, more effectively than if they are not done this way.
The softest Tai Chi and the Hardest Karate intermingle at those fractal points of similar energy flow. There is where the synergy of cross study becomes evident.
And sounder tactics are still more important than all of the above.
The funny thing is there are no shortcuts for any of this. NO clinic will ever replace long term instrution under a good instructor. No internet discussion will make anyone believe anything, you have to feel and experience it, and then believe it.