Hi Roger,
Instead of the in-line V-cleat, you might try the arrangement I have which enables easy, effective control in heavy air.
Above deck, the vang is the traditional 4:1 , but the tail then goes through the cuddy to a series of blocks resulting in a 15:1 purchase. The line passes back up through a through-deck block and cleat at the cuddy edge. Others I've seen cleat on a hoizontal bar under the cuddy, and also on the CB trunk lid. One thing I've discovered with this, though, is that the line should be small enough diameter for things to run smoothly.
Alternatively, and I swear I'm not a rep., West Marine sells a "Dinghy Vang" with lots of reduction which looks like it might do well on a DS.
http://www.westmarine.com/webapp/wcs/st ... ctId=62137Cheers