Hey there questioners
Here is what I have found with riding and helping tune the Monaro for Airush.
These boards are high performance racing machines, they take time to master, just because you have a fast board does not mean you will win races. It is very important to learn how to handle your race board so that you can get around the course at top speed and not go over the handlebars or blow up on the downwind.
The 22 and 18 cm fins sets have been coming standard with the Monaro, Putting the larger in front will help you point higher but will be harder to control. Putting the larger in back will be better for control but you will lose some VMG upwind. The width of the board has proved to be negligible, wider is better! Ideally you are riding the fins not the board, the board is just there for you to stand on while maneuvering or to help you through light wind spots.
It takes awhile to learn the ins and outs of what is going on with these boards, your body weight, wind strength, and skill all correlate with what size fins you can use. Although the 22 and 18 are almost big enough for me at 135 pounds, for larger riders they may have to kite size or even fin size up, and Airush is making more fins, PM me if you have any questions or concerns.
oh and hopefully this works, here is a GPS track of a training session in SF with Koch, Wasson, and Heineken, this was when we were still developing (we still are!) and the board was only marginally slower then their custom boards. http://connect.garmin.com/activity/28320718
hopefully it works.