I think if you get anyone else to do it, it will void your warranty?? Anyhow, the only other option I know of is to do it yourself. The the inside measuring knife edge of Calipers can be adjusted (and locked) to loosen the ring.. Would probably be better to just take the measurement you get from the caliper & make a tool to do it though.. Cut the metal to length, then taper it inward so it don't scratch the inside of the bell. I haven't done it in a while, (Never to a expensive scope) but if I recall you turn the lens counter clockwise to for closer range P.A setting.