SWIM prefers whole as well. Although SWIM works with large amounts of whole, shredded, and powder, SWIM seems to think that powder, although convenient, may produce a less-potent end product. SWIM knows for certain that although Psilocybin/Psilocin and DMT are two very different psychoactive compounds, Psilocybin will begin to oxidize out of powdered mushrooms within a matter of hours if left out in the open.