Nikkyo - absolutely, no pain when performed properly as a connective technique that allows for Kuzushi - same with Sankyo, although admittedly it's slightly more complicated with Sankyo. But quite possible. What is called for is the skill of connecting through to Center without "disturbing anything else" so to speak."
Ok, I am being a argumentitive.
To use the phrase "when performed properly" IMO states that if you are causing pain you are doing it wrong. I do not think I am doing my techniques improperly because they cause pain. Pain is a part of training IMO. I do not rely on pain as the sole motivation. Taking uke's balance is primary.