Do you have the guide tool? Not required, but it makes it almost impossible to get an uneven cut. Don't forget you'll probably need to move the star-fangled nut down, as after the slice it may not be far enough into the tube (about 15mm as I recall). If you don't have the additional tool that sets the height of the nut, find a bolt the same size as the top cap bolt, screw it in and hammer on that.

Good guide here: http://www.parktool.com/repair_help/...forksize.shtml