Y'know I can see where people are coming from with the opinion that opioids diminish the profundity of a psychedelic experience, but in my experience it hasn't always been so. Back when I was a kratom "chipper" (thanks corpus collosum for reminding me of that term!), before my level of pain actually required daily use of an opioid, I would sometimes take it during the come-down of a trip as it would ease me out of the experience and lead to a very relaxed and reflective state of mind. I have even taken kratom at the end of a Jurema-Harmala experience, somwhere around 8-10 hours after taking the harmala... which I DO NOT recommend as many people I have talked to have said that harmala and kratom leads to nasty side effects like extreme nausea, dizziness, and piercing headaches. These are all effects of taking too much kratom, and I believe these, excepting nausea, are likely due to potentiation of the other active chemicals in the leaf.
Since then, I have become a chronic pain patient and take an average of 50 mg hydrocodone daily, switching between that and kratom on some days. This has forced me to use them while tripping. I don't think it really diminishes much, but then I dunno I try to not take them till the end of trip. Still sometimes its not possible. Pain is probably just as distracting as a low dose of opioid.