Reefing Claw needed, or modify sail
I have a Day Sailer II that has the same basic set-up as your Javelin. To reef you would roll the sail on the boom as described, but the description contained a couple of errors. First, you do not move the mainsheet to the end of the boom, won't work. What you do is use a reefing claw, this is a "C" shaped fitting that has a pair of ruber or plastic rollers at it's tips and a shackle in the center. You unshackle to mainsheet block from the boom and attach it to the claw, next you slide the claw over the boom and roll the sail in to reef. You do need to remove the boom-vang if you have one, but the down haul should be left alone and in fact is still needed to keep tension on the luff of the sail. The downhaul is attached to the part of the gooseneck that slides in the mast groove and so does not need to be released for reefing. I tried the toller-reefing on my boat, but the sail really didn't shape well when reefed. I'd recommend bringing the sail to a sailmaker and have them add a set of reefpoints (grommets) to allow slab reefing (aka Jiffy-Reefing) and forget about the roller-reefing. I did that on my boat and the sail mods cost about $67. You don't have to buy a new sail to get reefpoints, they can be added.
