[wizard]

I have visited this issue as well, and the problem with going to a smaller pulley is that you don't get enough bite on the smaller pulley and the belt will slip (As explained by March tech). The correct solution is to go to a larger crank pulley. This will also increase your water flow and the "parasitic" load on the engine. But as stated very well previously above, the hp gains aren't worth it staying "underdrive".
(edited for typos and grammer - mwj)