T. K. Chiba
I practice aiki-style aikido with Yamada and Kanai Senseis. We never have done anything past gokyo; at least I haven't.
I went to a seminar several years ago. Chiba and Shibata Senseis were among the instructing crew. They're both Aikikai from the west coast. That's where I first saw rokkyo. I went to chiba Sensei's dojo and picked up a copy of his multi-volume video set. He does rokkyo all over the place in there.
It's a pretty cool technique.