I, too, have speculated about the relative effects of 4-phosphoryloxytryptamine (norbaeocystin) and its methylated homologues (baeocystin, psilocybin and aeruginascin) and their respective contribution to the activity of a mushroom. Were it possible at present, it would be my research project of choice. I've even gone as far as writing an brief outline of the idea. I guess I could post it here sometime.
Furthermore, SWIM can confirm also a clear qualitative difference between various species of mushrooms. Psilocybe semilanceata give more of a body electricity feeling and can give varying psychological/visual effects between different collection locations (different strains). Plus a factor with this species is that people can underestimate the potency of these small mushrooms, the physical and "mindfuck" side-effects perhaps being explicable as overdose!
Psilocybe cyanescens is SWIM's personal favorite - a fresh handful of those made into a tasty miso soup gives an unparallelled visionary experience! A noted side effect here was a fairly stong diuretic effect (large output of urine especially in the latter part of the experience), but other than that the somatic effects were minor. And as for experiences lasting only six hours, SWIM would beg to differ, having managed to get about nine hours of psychoactive mileage here. Before you ask, these were fresh, wild collected specimens expertly identified, with no chance of adulteration.
Psilocybe cubensis seems to give a pretty clear, clean, visionary experience, especially when prepared as tea from fresh specimens (maximum psilocin potency, viz P. cyanescens which also is far better when fresh). If I could remember a reference here it would be helpful - I read somewhere that some strains of P. cubensis produce large amounts of phenylethylamine, which can explain the cardiovascular/"speedy" effects sometimes felt.
Panaeolus subbalteatus gives a most pleasant visionary intoxication but SWIM cannot confirm the effects of large doses (where muscular weakness has again been reported) due to SWIM only having found a small amount and only the once.
Finally, the intrepid SWIM reports that an as yet unidentified diminutive tropical species of (probably) Gymnopilus (or possibly Galerina - SWIM is lucky to be alive, I must say!) gave a delightful, gentle visionary experience with no somatic trouble at all, at a time when SWIM was finding P. semilanceata to be quite troublesome physically.
I hope this is of some use. I think we should look at other components of mushrooms, besides the standard tryptamines, e.g. phenylethylamine, tyramine (perhaps) or other substances as yet unknown, which will undoubtedly contribute to their physical side-effects. In the realm of experiential investigation, however, it is rather impractical to perform analyses of all material to be ingested... it would require some careful note-taking and the preservation and analysis of a standard sample from each dose.