So very good to hear from you, Wilhelmus! It is wonderful how the tools of the web help us to find each other. Even though I am clearly outside the academic mainstream, my very first encounter with your work was with "Realities Out of Total Simultaneity" (goes to your abstract). And, of course, I thoroughly enjoyed your response to my webpage: posted on January 5, 2019
At that time, my wife and I were in the process of moving. I am happy to report we are finally moved into a new, smaller home and we are getting settled in.
By the way, I am glad to have your latest article from within FQXi: Your FQXi article I'll start going through it most carefully.
Now, let me address your comments and question, "...what is in-between these spheres?" First, I never thought to ask! And quite possibly, there is a little less than nothing, not even the aether. Yet, within a few notations, I would guess that tetrahedrons and octahedrons begin filling all the space created by those planckspheres. Let me give a bit more thought... perhaps I can come up with a more satisfying answer. Thanks for asking! -Bruce