I have a Cheoy Lee Offshore 27, and it has boom roller reefing. I also have one of the boom claws that are mentioned here, meant to be used to vang a boom that is roller reefed. Aside from being ugly (it''s bright yellow) I had serious concerns about the chafing that might occur when the main is reefed. Nontheless, I wanted to test it in a nice December blow on Long Island sound. Wanting to try it myself, I gave the helm to a friend when the rail went under. We were on a starboard tack and the roller mechanism in on the port side of the goosneck fitting, so hanging off the underside of the boom I tried to manipulate the roller handle to get the boom rolling. I dropped the handle in the sound. We jiffy reefed, and I have since never taken the time to have a new handle made. I use the handy billy that came with the claw, but have bolted a U-bracket on the underside of the sail and vang in the traditional manner. No roller main for me.
Theoretically, the boom claw works just fine. It is what you are looking for. I''d be happy to part with it. E-mail me at firstname.lastname@example.org and I''ll mail it to you. Just pass along a favor when you get a chance...