Distortion of the solid earth is well known to those who make sensitive
gravity measurements. They have to make a correction for this effect. As I
recall from a geophysics class 25 years ago the tidal correction is something
like 0.01 or 0.02 mgal (g = 980 gal). (Another advantage of non SI units. You
can type them in e-mail) At any rate I think this kind of variation in g
would require a distortion of the earth of something like +/- 0.1 to 0.2 m.
If somebody is on a campus where someone is acturally involved in gravity
research I'm sure they would serve as a more reliable source of this info.