Denny, is this because you just believe that a sub-hallucinogenic dose is just too little "medicine"? I guess my question here is just clarifying important semantics. To me, "sub-hallucinogenic" means that something might happen (or nothing might happen), but it's not a full-blown trip experience. So I'm asking whether you think a trip experience is essential, not for the trip itself but because that's the only way to get enough psilo? Or do you think a sub-hallucinogenic dose, with some effects, just not "hallucinations," could be okay? That's what Bob W is saying in the next paragraph, and Dr. Schindler actually uses the word "non-hallucinogenic" below to describe some successful busts.
Here's Bob, from last year, saying that the the right dose is going to be sub-hallucinogenic: somewhere between no effects and a full-blown trip: "The small doses of psychedelics used to treat cluster headaches are usually enough to produce some felt effects, often described to me as a two-beer buzz. But these are still far less noticeable than the effects of a recreational dose." https://blog.petrieflom.law.harvard.edu/2022/04/18/small-doses-of-psychedelics-for-cluster-headaches/
This is Dr. Schindler [the person conducting the Yale research] reporting on the results of a 2015 CB survey of 496 people: "...infrequent and non-hallucinogenic doses were reported to be efficacious." https://pubmed.ncbi.nlm.nih.gov/26595349/ (To me, non-hallucinogenic and sub-hallucinogenic both mean the same thing -- no "trip.")
More from Schindler (https://americanmigrainefoundation.org/resource-library/can-psilocybin-treat-cluster-headache/): "Researchers also discovered that for those who found the psilocybin treatments effective, the degree of symptom and pain relief was not directly related to the strength or intensity of the psychedelic experience. This indicates that “the mechanism [of cluster headache] is probably not directly related to the psychedelic experience itself,” says Dr. Schindler. “That’s in contrast to most studies in psychiatry [involving psilocybin], where the bigger your experience is on the test day, the greater your improvement weeks and months down the line.”
Way back in 2006, from one of the Sewell/Halpern/Pope publications: "...given the apparent efficacy of subhallucinogenic doses, these drugs might benefit cluster headache by a mechanism unrelated to their psychoactive effects." https://www.semanticscholar.org/paper/Response-of-cluster-headache-to-psilocybin-and-LSD-Sewell-Halpern/e9aec20b22da4b258365f1e21d17ac3c62a48899