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.

@lewm 

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.

You are exactly right.

Just measured another one for fun This was a 158 gram Hickory. The thickness of the grooved portion ranged from 0.053" at the beginning of the first track to 0.063" at the end of the last track. This means that the top surface of the LP will be at a 0.18 degree angle if it’s laying on a flat/level platter, or your azimuth will be off by 0.18 degrees if you set azimuth with a mirror on your platter.

That’s a lot. I just had two precision shims next to each other that measured 0.0 degrees and 0.12 degrees, and it was very easy to see the difference.