LP Thickness/Taper

I find your picture interesting in that the outer rim is not resting on the turntable platter. Since the rim and center are considerably thicker to suspend the playing surface off of the platter. And I would imagine that the 180 gram pressings have different relative thickness between the outer grooves versus center playing area.

My guess is that the pressing process plays an important part as the puck is pressed from the center out as pressure is applied. Maybe the bulk or mass of the puck causes a restriction equalization of pressure across the diameter. Although I would also think that the manufacturer of the press would have accounted for this after all these years of vinyl manufacturer. It would be interesting to run this same experiment on records based on the manufacturer of each pressing machine. 
Kudos to you for taking time to do this, but although I don’t see that your motive is my curiosity, but I find it intriguing none the less.

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. Once again I am reminded of an article which I think Michael Fremer wrote about the playback of vinyl contradicts logic on many planes. But thankfully it does it as well as it does.

thank you for this food for thought 

ketchup, I can appreciate your logic concerning the mat you have and I agree on a hard mat that makes sense as the only way to go. However I have a felt mat on my Rega and would think that the vinyl rests with a fair distribution of pressure across the playing surface. In addition to that I have recently added a Michell clamp to my TT and hope add to that equalization of pressure. I do realize that the raised edge and lable area have been on records for as many years as I can recall, of course that practice goes back to the days of stacking records on automatic turntables. A practice that hasn't been used for decades, so it kind of suprises me that modern day records are still pressed in this manner. But I guess it does drastically reduce the chance of the stylus exiting the record off the lead in. 

But again at the end of the day, I appreciate the time and effort you spent pointing out the variance in thickness. I found it mind provoking in the physics that a tonearm and cartridge must overcome in revealing the information found in these "somewhat" flat peices of vinyl.