Use red loctite to secure hex nuts to the follow focus ring gear mounting grub screws. Be careful to not get it on the portion of the screw that goes into the ring gear if you want to ever remove it. Allow the loctite to cure for an hour and then thread them into the ring gear. It can be slipped over the front of the lens and the hex nuts spun by hand until they contact the focus ring on the lens. Tighten alternate sides until snug.