I agree with Hugh here in several areas. Back in the mid 70's I took some ukemi from Tohei Sensei, went through the ki exercises presented at the time and can see that the 4 principles that he talked could be connected with the solo exercises from Dan that are being worked by many of us now could be aligned with the 4. The problem then was there was no explanation, at least with the folks who I can in contact with.
That's usually the crux of the issue with Tohei Sensei's methods, I remember the problem well, my teachers kept telling me to 'keep one point' and I kept saying 'how?' The truth is the four principles are not the whole story so much as a condensation of what you need to do and an aid. He also has principles for doing aikido. Tohei Sensei's 4 & 5 principles are these:
4 Principles for unifying mind and body
- Keep One Point
- Relax Completely
- Keep weight Underside
- Extend Ki
5 principles for doing aikido
- Ki is Extending (Extend Ki)
- Know your opponent's mind
- Respect your opponent's Ki
- Put yourself in the opponent's place
- Perform (Lead) with confidence
If I translate (based on my best understanding of course) into IP/aiki speak the four principles, they become
- Keep One Point - initiate/coordinate from dantien/silk reeling
- Relax Completely - do not oppose force, allow it to be redirected through your body, shoulders are a big issue here
- Keep weight Underside - use elbow power (that one is a bit vague, sorry)
- Extend Ki - manifest 6 directions
Further, there are three basic levels of ki tests, level one involves having basic physical coordination, you might draw a parallel here to kokyu-ho which are some of the methods you use to develop this basic level of coordination for such a ki test. The second level is to have a relaxed mind, which is to say if the tester applies a hesitation before touching you, you should not flinch or move, because you should not be anticipating the test. The third level is to not allow the testers ki to enter your body (bit of a misnomer if you ask me), it's fair to say that this level is where you are into redirecting force within yourself. An example might be if a tester pushes on an extended arm via your hand you should not allow that force to be transferred into your shoulders but into the floor. You have to have a relaxed elbow to do this, in other words, you must use peng-jin. In Tohei Sensei's system you must have passed tests on all three of these levels to get shoden in ki development, there are several ranks above and beyond this which should tell you something, obviously there's more to get on to but the details of that are not so clearly formulated as the first three levels of development.
Practising Tohei's methods has a tendency to leave bits of you stiff that shouldn't be, so you can develop terrific static power doing it, people can push on you pretty hard and nothing will happen. But it tends to encourage you to shut down movement because the teaching structure involves half and half ki and aikido. So you spend an hour or so learning how not to be moved, then another hour applying that to movement and waza and what you get is stiffness for want of a better word. I see lots of people brought up in this school (including me) who don't move their feet enough.
Also there is a tendency I've observed, to use this power to try to physically overcome an opponent, its quite common to see people brought up this way use peng-jin type stuff to more or less just drive over a partner like a tank. Being completely insensitive to what their partner is doing and only interested in flattening them. This is, IMO, technically not what Tohei Sensei was after, just an unfortunate side effect of the pedagogy used. Which of course means that pedagogy needs to be changed.