Julien,
A Kiter from our group just got a North Race LTD board. The board is fast but best of all is an upwind machine he is an experienced kiter and he likes the board a lot.
For the race, check first what the windsurfers are using, are they racing in big boards (150 Liters and up) or are they racing in small 115 lts and so. Is the race course a simple reach or has an upwind leg or a big down wind. That should determine your type of board and kite size for the race. Also think in learning on your first race, and wining on next year, there are a lot of dedicated windsurfers out there that I am sure they have the race, weather, and equipment well dial in for race day.
Best of all have a great time and race comfortably.
Arturo
Kitesurfer México