Unfortunately, given the nature of EUROPE as a whole comprising different countries each with their own IMPORT REGULATIONS and well as EU REGULATIONS being interpretted differently by the respective EU MEMBER COUNTRIES caution here is indeed warranted
Even where a substance is perfectly legal for import it has been known for CUSTOMS officials to be overzealous and hold the item... I think the saying "Better Safe Than Sorry" applies here
Therefore, how I would propose that we handle the shipping to EUROPEAN participants is that BY DEFAULT I will mail out the PRL SAMPLES in the same manner in which I dispatched the COLURACETAM samples, wherein anyone can OPT OUT by sending me a PM MESSAGE requesting as such, in which case the package (including its CUSTOMS DECLARATION FORM) will instead be labelled specifically with its SYSTEMATIC NAME; however, please kindly note that in such instances I cannot be held responsible if your country's CUSTOMS seizes the package. It should be noted that a couple of people chose to do this for their COLURACETAM sample and whilst one person did receive his, the other DID NOT and it is my understanding that CUSTOMS seized the package, even though it was not appropriate for them to do so
The package in all instances will be labelled "SAMPLE - NOT FOR RESALE" so as to distinguish the fact that it is NOT a commercial item; and I would recommend that Q does the same for all the packages that he dispatches (wherein he likely already intends to do this)
why not send it as a personal letter, in an envelope with hand written name and address, just like some random letter? there's such a low weight of the substance it would fit in a letter envelope quite easily and i doubt any customs would open that?