in my experience, which is quite small at this stage, the only good result I've had with yonkyo is with the nerve pinch.
I have always been taught to use the nerve, mainly to get uke to lift up and change their body position without really any effort on my part, and then follow through with the rest of the technique. I have not been shown any other way (as yet), and the times when I have not hit the nerve on the thick wristed fellas, they have not moved.
I have trained with one person where he did not feel the pinch at all (one of the rubbery folk), even the Instructors had a rough time moving him, but I found he was very suseptible to Ikkyo and that was the only way I could get him to move. It was quite hilarious watching the instructors face when I moved him during kata-tori-yonkyo, although I had applied an ikkyo.
Even I myself have not been moved without the pinch, but perhaps that is just the way we have been trained, or I have not yet got to the non-nerve pinch yonkyo.
So for me, yonkyo requires pain, very briefly, but just enough to lift the uke and have his balance. I have trained only once in yonkyo to excess during a seminar, not nice!!
Now, once we have found the nerve once, that's it, no more until the next class.
I am enjoying reading the yonkyo threads, very interesting.
Different strokes for different folks??
or different methods of training??