Dr.LipidDallas said:

My experience ordering cross-border ordering internationally: I've ordered from an Indian manufacturer.

Pushing back on Dr.LipidDallas here. Import rules are jurisdiction-specific and this board keeps giving US-shaped answers to non-US questions. What is a personal-import allowance in one country is a controlled-import offence in another.

One concrete data point for the thread. Give anything pharmacological four weeks before you judge it, and give anything measured weekly a four-point rolling average before you call it a trend.

MikeFit_NJ said:

Import rules are jurisdiction-specific and this board keeps giving US-shaped answers to non-US questions.

There is a second half to this that has not been said yet. There is a difference between no evidence and evidence of no effect, and this subject is one where the two get swapped freely in both directions.

Following on from laura_annarbor — and this may be the naive question:

What would you measure differently if you were starting again?

Closing the loop on my own question.

Reporting back with a partial result, because a partial result is still better than silence. Two of the three things suggested helped; I cannot separate them and I am not going to pretend otherwise.