LP Thickness/Taper

@theo 

I find your picture interesting in that the outer rim is not resting on the turntable platter.

Many turntable platters are designed like that because the outer rim of the record is much thicker than the grooved portion.  By hanging the thicker, outer portion off the platter, better contact between the record and platter is made.  That's an old Goldmund Relief Mat. It looks like they chose the perfect diameter as the LP begins to get thicker right at the edge of the mat.  In fact, the entire mat fits the LP like a glove.  It perfectly matches the contour.  It even matches the stepped portion of the label area.  It's more apparent when the image is viewed full size.

However if I interpret your motive or question. I don’t know how a tonearm setting can be set to anticipate and compensate for this variance.

Any arm with adjustable azimuth will be able to compensate.  You just need to figure out a way to adjust azimuth while taking that 0.12 degrees into account.  I've figured out a way to do exactly that and will be testing soon.

I always check azimuth in the middle of a thrift store record. And several 1/1000ths of an inch matters not! Not in the real world!!

I always set all cart adjustments with it aligned exactly half way in the middle of the record. On my VPI Classic TT it specially matters for VTF and anti skate. But it would also be beneficial for azimuth if all records are built like the one you tested, which I doubt. Anyway, to test a cart alignment either at the beginning or at the end of a record makes no sense at all. Always test the middle for the best average adjustments. 

Since the angle of incline appears to be constant from outer to inner grooves, seems to me if you set azimuth correctly at any point on the LP surface, there would be no problem related to a changing azimuth angle.

Another vote for the middle.