Briefly speaking,
It sounds brilliant and fascinating. Good luck with it.
Just another thought. I know this attributes gravity to mass, but, consider
this:
As one would enter the earth's crust, the deeper one got the less mass there
would be underneath one, especially if the earth is hollow. At some point
there would be a certain amount of mass above one as well as beneath.
However, the actual greater amount of mass at a certain depth would be to the
sides rather than below or above.
In a latitudinal alignment this sideward mass would remain rather constant to
either side. But, in a longitudinal alignment, considering a certain void
where a polar opening would exist, the greater mass would be toward the
direction of the equator. This might account for a 1/6000th divergence in
the sway of a plumb line in itself. Let's see, from the equator to the pole
is one-quarter of the circumference of the earth, or approximately 6000 miles
of the earth's latitudinal circumference. A mile distance between two
latitudinally aligned objects then would have approximately a 1/6000
difference in the amount of mass that would be influencing this sidewards
gravitational influence. Hmmm. I realize this is an oversimplification,
but, it demonstrates a concept where the alignment of the lines and the
tunnel may be another possible unknown factor in explaining the oddities of
the experiment.
Just a thought.
Norlan