watch out about how you cut the...white spacer thing. if you use a saw or something, you'll lose a large (compared to the spacer length) amount of spacer. i'd suggest using a steak knife or something...then again, i'm unsure of how hard the spacer is. or find somewhere with spacers, and then make your own to specific lengths. just make sure hat you conserve the total spacer length both before and after cuting.
well, i hope that made sense, cuse it doesn't sound like it did.