It turns out that 12.5 knots down wind is a bit too fast. The rhythm we had at 10 knots changed. The waves roared and splashed up over the stern and into our cockpit, the wimpy little auto-pilot became erratic and the boat got too noisy. At 10 knots we could all relax. Maia could play with her dolls, Charlie the cat was content, Evan and I could read. So we slowed down.