Before the final race on the Attersee we tested the wind at three-minute intervals (as we always do), and about one minute before the start we recognized a huge back of about 25 degrees. We continued down the line, started on starboard at the pin, realized we could tack and cross the fleet, and did so. As the rest of the fleet realized what was happening, they tacked and followed. We were 150 feet ahead of our nearest competitor and pulling away, until we sailed into a soft spot and the fleet, now lifting on our hip, began to close. We tacked to cover, but immediately recognized that we were going against the shift by doing so. So we tacked back to port, preventing the loss of all but four boats and snagging one back.