Boat rigging ideas undergo
continual evolution. An earlier How-To detailed a boom vang that came from the boom to a block that ran free on a rope bridle planted on the foredeck with the ends terminating 8 or 10 inches outboard of the mast. It was tensioned by a continuation of the line from the running block, up to a block on the boom three feet aft of the mast, then down to direction changing blocks on the mast, to a drum winch below decks.
This variation takes the line from the boom to the block running on the vang traveler. Tension is increased by pulling on one end of the traveler from under the deck, either with a drum winch or a block and tackle system. Simple and effective. You already have a power of two by pulling on one end of the traveler, with the other end dead-ended. In effect you are lowering the boom by lowering
the bridle traveler. Further benefits are that no fittings attach to the mast and there is less clutter around the mast at the deck cutout.
As with the earlier version, this vang not only jibes without adjustment, but holds the boom forward as well as down.