Here is a movie of my Rhino-Beest model (so far). Looking at the video of Jansen's Rhinoceros, it appears that the six leg pairs (front + rear = pair) each have separate cycles. I decided to simplify the task of boning/constraining the model/action by making 3 pairs of bones/constraints and assigning CPs to leg bones so that the legs move symmetrically on either side of the model centerline.
The action is driven by bones M1 through M6 which rotate around a common center and each move one of the leg mechanisms plus its respective CP doppelgänger. The walk cycle that seems to best resemble Jansen's Rhinoceros has pair M1-M2 (front-rear) set at 40 degrees apart, then an 80 degree gap followed by M3-M4, etc.
Thanks again to Robert and Serge.