Vselimaj, the fact that you are a Stoic practitioner and use psychedelics does not imply that Stoicism is logically welcoming the use of hallucinatory substances.

Because that's what those substances are. They don't show you a new or different reality, they make up things. And during use you are not in charge of your reason, which is the most precious thing we have according to the Stoics.

So no, I don't think the Stoics would have embraced psychedelics had they known about them. Indeed, they did know about them. Several "mystery" cults and religions used mind-altering substances in their rites, and there is no trace of endorsement by Stoics of such practices. The only possible exception of Marcus Aurelius, who allegedly was initiated into the Eleusinian mysteries. But the reason for that is probably because that was one of the things he had to do as an emperor, not as a Stoic.