@Cary L Brown - I'm going to have to disagree with you about not being able to see the diagram clearly enough on screen as the top view gets a decent close-up in "The Enterprise Incident".
947' was the working size I had picked because that was as good as a place to start and I knew I might need to scale up from there. But up until "The Enterprise Incident", I had not considered it to be a number that can be derived.
I am attaching 947' size to only the "diagram version aka pre-Pike version". I'm still going to end up scaling the Series ship up to fit the flight deck and not because of interior set issues (which I have yet to find except for the flight deck).
Funny enough that you mention how would a Thermian know what the measurement for a foot would be... simple, use Miss Lincoln from "Assignment Earth" as the reference
You can see the diagram, TODAY, on a HD screen, on BluRay.
But in 1966, on the best possible color TV set, there was no way you'd have ever seen anything from which you could derive anything CLOSE to the sizing.
I know, we're looking at it as though this is all gospel, but again, remember, the sick bay monitors in TNG had one of the indicators which showed "insurance remaining." This was never intended to be seen, but it was there.
The images seen in TEI were, as far as I'm concerned, along those same lines. Intended to be recognizable as views of the Enterprise and the D-7A design, and to show rough proportion between the two. But the ships shown in the diagram aren't the ships seen on-screen, just "rough approximations," and the scale is NOT clear enough that, without leaping through hoops that no one on the original production crew could have ever imagined you'd be leaping through, you could ever arrive at any reasonably approximation of the size of the ship.
On a late-1960s TV set, you could only see the basic shapes, and see that there was something which was probably a scale bar, in that diagram.