hy this method was heavily used into inspection areas, that used to use sets of gage pins with increments of 0.01, 0.005, or even less; required hand's sensitivity
method was tough, but it started to loose ground a few decades ago
what you did is ok, just keep it up if you like to go that way
if you wish to go futher, "down the hole", then try to think about calculating a diameter, using :
... 3 points from a ( normal ) probe
... 2 points from a probe that is sensitive to cosine directions / kindly