I use a modified sort of preventer set-up. I rig a pair of four-part tackles, with cam cleats on the bottom blocks, to a mid-boom bail. One tackle leads to a port mid-ship cleat, forward of the boom and one leads starboard. To gybe or wear the boat in heavy air, I can loose the weather preventer, and haul in the lee as I steer with my legs on the tiller. I use the mainsheet as a boom brake to fine tune the process when I am on my new broad reaching course.
This differs from the usual preventer-to-the-bow and back set up, but it's worked for me in 30 knots. Here's a picture of the set up prior to hoisting the main. I suppose you could call it a "split vang", as well, except that these are rigged for the whole day of downwind sailing.