I cut mine. Its not too difficult, if you measure and make straight cuts, its tougher if you try to make curves. Balance just like you would balance a propeller on the mag balancer, you have to mark the backplate to ensure balance when installed. Its not as critical on the small spinners to get it "perfect" because there is so little total weight so close to the center, its got to be pretty far off before noticable vibration ocurs.