This question lacks an answer that can actually be taken seriously. As many of us know, the therapeutic index of Opioids, for lack of better phrasing, is not ideal. The dosage required for analgesia is not far from the dosage that will cause blissful intoxication, with this dose being proverbial inches from the dosage that can kill through respiratory arrest. So, not only is it pretty difficult to estimate the "right" dosage, it's actually very irresponsible to suggest to another individual that a given dosage will not kill them.
Hey, if we're talking, "what is within the realm of safety", we can typically do that. When someone says, "I'm feeling it, but I want to be higher", it becomes irresponsible for us to suggest anything other than their current dose, as what we know about Opioids implies pretty clearly that they are dangerous, potentially deadly and highly unpredictable in many cases.
What works for one person might not work at all for another person and we really need to keep that constantly in mind.