C:

Petrie adds a comment that, possible coincidental but, the level of the Kc chamber floor is the point where the cross-sectional area of the pyramid is one half that of the base area.
Added to this are his personal measures of the interior.
Compare the center location of the chamber points with the upper point of the ascending passage.
The illustration below gives Petrie's recorded measures.


Personally, I think it was easy for the builders to reference these two points, but I do like the sqrt of two coincidence. The reason?

For the floor of the Kc to be at a level where the structure's area is half that of the pyramid base it must be located at a point where the base width is the "square root of 2" compared to the chamber !!

Best.
Clive