I think Gebi meant to say rocker.. rocker will help in the chop, concave not so much. Longer is definately smoother in chop... but you risk digging the nose... there is only one magic bullet in a down wind race... a big board with some rocker if it's choppy, a big kite, and no fear... because you are going to need to be hauling a$$ if you are going to win, and that means being uncomfortable and on the edge of control.

Last year I found the best way to go (directly) down wind (in a hurry, it's a race after all) was to figure 8 the kite... dive hard, bring it up and around and dive hard again the other direction... as fast as possible. Carve a mellow S back and forth straight down wind... basically going back and forth from backside edge to toe side edge... never let the kite stop moving... edge only enough to keep the kite flying and powered without stalling.

You don't want to be pulled by the wind, you want to go faster than the wind..

Most people rigged 9's last year... I rigged a 13 and worked it hard going straight down wind. I wish I had rigged a 15 or an 18 and ridden a bigger board... I finished in the top 15 but I could have done better if I were more powered and hadn't wasted so much time at the start.

This time waves and chop are involved, plus you are going straight down wind, so you are going to need to rig a lot bigger than normal if you want a shot a winning. Your legs are going to be useless towards the end.