Cutting the slide is easy. Take the needle out, and stand tghe slide up straight on a flat surface. You will see that there is an oval "cuttout" on one side, and the other side will touch flat to the table. What you want to do is to make this cuttout taller, but not wider. Take a permanent marker, and mark a line across the surface above the cuttout where you are going to cut. Now, take a caliper and lightly scratch the surface at the amount you wish to remove, and trace this line from corner to corner of the cuttout, tapering it at the ends to meet at the same corner that exists now. Grind this portion out, then sand the edge clean of burrs.
I can't tell you how much you might need to take off for your bike, but 1mm was perfect for mine.
If you screw it up, or you don't want to attempt it, you can buy leaner slides, but they are pricey. The dealer wanted $90 for one for my bike.