Hello C. Wayne,

As I have just posted to Poundr17, I have a growing feeling that this 'close to 70rcs' is the natural product of something else.
To try and find some possible candidates for this 'something else' I've gone back to square one, which in this case is Cole's 1925 survey.
So far I have established (at least to my own satisfaction) that the mean distance between the north and south sides of the Pyramid's base measured along the mean line of the axes of the passages is 9069.87".
I've assumed the inclines of the north and south faces to be 51:50:34, which puts the apex at 4534.98" from the bases of the north and south sides.

It is also because, as you point out, 'the shafts were not positioned at the vertical quarter-points' that I have growing doubts that 70rc was the target, so to speak.

Regards,

MJ