Proper measurement of stock dimensions

[Double Trouble]

Is there a specific "standard method" to measure stock dimensions ? Specifically, drop at comb (DAC) and drop at heel (DAH).

Here's how I measure them: Using a straight metal ruler, I lay it NEXT to the front bead, along the top of the rib. Then I measure the perpendicular distance from the ruler to the front-most part of the comb (for DAC), and then do the same at the "spur" on the Parker buttplate (for DAH).

Is this "right?" My letter claims my Parker has a DAH of 2 7/8", but in order to get that measurement, I need to measure it approx. 3/4 of an inch forward from the buttplate spur.

What is the proper/standard way ?????

Thanks guys !

John