Digital force gauge query

Hdm:
I think your advise is spot on. I measured with the mat off as a means to compensate for the thickness of the gauge's measuring platform. I am using the exact same gauge as you, i.e. the Carong. My question is why, scientifically, even logically, should the readings differ merely because the plane of the arm is at a slightly different angle?

I measured my Mystic Mat against the platform of the gauge with a ruler and found them to be essentially the same height. So, to my way of thinking, these eseentially cancel each other out, i.e. placing the gauge directly on the platter is the equivalent of where the stylus would otherwise meet the mat. In order to allow for the height of a record, I removed the mat, placed an average weight record directly on the platter and placed the gauge on the record, measuring for the optimum VTF for my cartridge, which is 1.8g. Seems a logical solution.