personely i hated reed spacers... i tried them both on the front side of the reeds (pulling the reeds back 1/2", & on the back side of the reed pulling my carbs back 1/2" & it really changed the power band. i do have to admit they did give me a bit more bottom end on the front side of the reeds but i'd never put them on again ... i love the way mine works with Port-job, Pro Circuit pipes, FMF Ram Valve Reeds, head shaved .030", UNI filter, NGK Iridium plugs (best plug ever, ran them all summer & still have them in).
but it all comes back to how u like them there only cheep, i got mine of my cousin for a trade for a few other parts but ... i think there only cheep. so i'd say try them see if u like them i know i didn't.