Now we are getting somewhere, and I can now support what you are saying.
This is what I meant when I say 'the image is there' - you say 'ideal template', so we agree that what I have simply illustrated was intended . . . but of course there is more in what you say about Metaton's Cube and also the internal chambers of the GP in cross section.
Ok, so far, so good. I'm looking at it, and crystalising this in my mind by going over it and by making my own drawings.