I'll always use overlays on close call. Another thing, as an RO, you can't get upset it when a shooter calls for an overlay. IMHO, they paid the match fee and deserve a fair, accurate call. I've had calls overridden by the RM at big matches; so what. I'm trying score and keep the match moving as quickly as possible, mistakes can happen.
A beef I have is with a RO who starts trying to tell the RM what he scored and why. NO! Let the RM score it, that's what you are supposed to do, not sell him on your call.