I have a .pdf of a great side cut plywood board design that works really well. I put it under files in the arc users group. I have a number of boards and this one is my favorite. Really solid finless riding. It seems to handle a lot of power too. Try it. You won't believe it!
Here's the spiel for what it's worth: The key to a light wind board is to maximize the flatness (no rocker) to provide more surface area on the water and to eliminate the fins to reduce drag. This board has zero static rocker combined with the significant flex of the plywood which provides a dynamic rocker (more power, more rocker). In light wind the board is almost flat and provides maximum surface area on the water. When the board is powered up the flex adds rocker as you need it. I have been riding a strait rail version of this board for quite a while. Although it had great light wind performance, it was a more technical ride because of the looser (lower) turning input. The side cut provides more pressure on the ends of the board and less in the middle. This translates to more turning pressure which give a more stable feel, as if the board had fins. In addition it amplifies the dynamic rocker characteristics (less force in the middle) which gives the board more upper range.
The flex of the material used for the board is important. The conventional materials used for production boards (carbon fiber, divinicell, etc.) might be to stiff. Stiff boards are great with rocker but you need flex with flat boards and you need flat boards for good light wind performance.