I have a question. How do you get under if you can't physically get any further under? This is really hard for me. and probably many others too.
You drive them up. http://www.youtube.com/watch?v=QMHuWiIquTM#t=0m18s
is a video of me doing suwariwaza ryote dori kokyu ho. I drive him up, once his center is above mine, he's "floating" which makes it easy to move him away from me.