I would also encourage you to read up on the subject. Terence McKenna does an excellent job of examining the psychedelic experience. Some excellent books of his are "Food of the Gods" and "The Invisible Landscape." Beware to take his theories with a grain of salt, however, as he doesn't always manage to keep hold of his objectivity.
This is indeed the trouble with many psychedelic adventurers: the inability to remain detatched from the experience, critical but aware and involved. It's a delicate counterpoint, and one that I don't claim to have reached.
8 grams is truly a heroic dose, but given the relatively low toxicity of psilocybin the biggest danger would be a "freak out," because of the intensity of the experience.
As has been stated, there are quite a few threads where the question is discussed in depth, with some relatively good criticisms of psychedelic use written by the now-absent Froclown. You would do well to read up on them.
Remember that the Temple of Thelema does not condone or advocate drug use of any kind. However, students are encouraged to explore their psyche to the fullest. 😉
"The Doors of Perception," by Huxley, is also an invaluable read, and should be studied in depth.