Very interesting article. I've passed it on to other members of my dojo.
Something caught my attention, though. You say,
"In common, everyday thinking, the word tenkamuteki (which the Founder used when speaking with me privately during my teens) refers to being 'invincible' or being of such incredible strength that you have no contenders."
Can you say something more about your experiences with O Sensei? Thanks!
If you read the article again carefully, you will see that Ledyard Sensei was quoting Kanshu Sunadomari Sensei in the paragraph you referenced. So it is Sunadomari Sensei who was talking about his personal experiences with O-Sensei.