It seems to do the trick.
Even I understand it now from your Model. Before I knew the theory and that your cards worked, but on my daily 14,000 steps I have had time to ponder as I paced my quaterdeck, and could never quite grasp a mental picture of the process in my head, so you have cleared it up superbly for myself at any rate. Now I will have to go back to playing mental chess games whilst I walk.
Rob.