Sure, that could limit the generalizability. Aspects of the sample may reflect all the board racers out there (e.g., those not made [edit—ordered, I should have said] by TB).
But that being said, while TB gives Aero their desired measurements, the tag is determined by the Aero craftsman when it the jacket gets made (I assume). Aero is still the one looking at a jacket and saying “yup, let’s call this a 40.” I imagine TB orders them in a similar manner compared with the individual consumer, just in a much bigger volume (than some anyway—I’ve seen the size of some of your collections here). So these jackets, even those made to TB spec, still reflect what Aero deems within the suitable tag size range, presumably. I expect that the TB sample closely mirrors the general population in PTP, hem size and shoulder length, though I don’t have the data to actually show it.
Like I said above, the purpose of the exercise is to help answer “what does a tag 40 mean?” and related questions. I don’t think the limitations totally negate the findings.
Not quite. I don't know if you've seen what an Aero spec sheet is like.
I just feel bad saying much because you clearly spent a lot of time and effort on this to make a splash but unfortunately you went in missing some initial context.