I've looked at at least 5 different single line reefing systems. 3 of them use some sort of sliding block system inside the boom - which I still haven't figured out what it does. They vary in complexity from the Harken #430 system (Z-spar has a similar system) with 3 blocks and a fairlead, to the Catalina 42 system that uses 7 blocks to do apparently (to me) the same thing. All of them, for a 100# pull on the reefing line, pull down on both the luff and the leech with 200# (ignoring friction of course, which becomes a bigger factor with more blocks).
Biggest issue (at least for me) is to get a line leading from inside the boom through the gooseneck and up to the cringle in the luff. My gooseneck (Kenyon K-43006 on an E-section boom) currently leads the line from inside the boom, through a cam cleat, then over a block and down. The cam cleat goes away easily, and drilling a new hole to bring the line under the block isn't hard, but getting the line to go up involves removing significant structural metal from the gooseneck. Perhaps if I give Rig-Rite a call? New gooseneck castings from folks like Selden have much more flexibility as to sheaves leading up or down.
Current thinking is to modify the gooseneck to allow one line to go up. This will allow me to install single-line reefing at least for reef #1, which certainly gets the most use. I then see 3 lines coming aft - halyard, reef #1, and clew line for reef #2. I'd still have to go to the mast to put the luff dog-ear for reef #2 on the hook, but I don't do that too often.
Comments? (Please!!)