Since POI would change somewhat from one shooter to the next (thus the assessment by the expert that it shoots low only applies to him), wouldn't the pattern testing have to be done in the manner of rifle sighting to determine if barrel regulation, bent barrels or mis-aligned chokes be the problem? In other words, eliminating the vagaries shotgun fit from the analysis.
Drawing from personal experience, I shoot a double with a bit of cast-on, righthanded. My cheek climbs the comb so it shoots noticeably high, even though the DAH and LOP are on the money.
Its incredible what a small variance the the choke are make to POI. I bought a Model 12 with a Cutts Compensator (popular 1950s skeet set-up),took it to the range and missed everything. Due to the choke device being off just a tad, it shot almost a full pattern width low at 25 yards.
