im not sure a durometer is the correct device for measuring pool cue tip hardness. im an engineer and work with plastics alot in my industry and the duramoter is a commonly used tool. the issue with measuring cue tips is they are layered and there are different densities throughout the tip. as stated above it is more practicle to measure multiple points and even then, the irrregularities can only distort the test results. another issue with this is we would have to know more about the quality control of the manufacturing facilities. this is where we would need samples from multiple batches/production runs.
im not trying to overcomplicate things or dismiss someones work its just my experiences taught me to overanalyze in the pursuit of logical problem solving. this aids me in my work to prevent failures in our products.
Moori weighs each tip and considers the heavy ones to be the hardest and grades them accordingly.