I am a Grasshopper dealer, and, owned several for my mowing business before I became a dealer. The deck comes from the factory with the correct pitch, and the dealer should check that before he delivers a machine to a customer. The deck does a real nice mulch job with the mulch kit AND the correct blades. Mulch blades come with the kit. Do not use hi lift blades of any knid with the mulch kit. You can use the Grasshopper, "Contour", blades, or the low/medium lift blades. One of those two styles come with the kit.
The hilift blades will cause the deck to load up with grass to the point the machine will stall. They do not let the deck drop the mulched cuttings into the lawn. The other two types let some of the mulched clippings continually fall back in to the lawn surface.
You can use Gator blades when mulching leaves if you want to turn them totally to dust. However, the blowout will place most of that dust on you. I never found it necessary to use anything but the two types of blades recommended.
