Best Centerboard Designed Boats
Regarding the stability question in the original post, as Jeff says most boards are only slightly heavier than water, and so do not significantly lower the center of gravity when in the lowered position. There is a school of thought which says that a centerboarder is more stable with the board raised in heavy weather; as Jeff mentioned this allows more leeway. In theory this reduces the chance of the boat "tripping" over her keel. I personally am a great fan of centerboarders. Partially raising a front pivoted board moves the center of lateral resistance aft, thereby reducing weather helm, and is very useful in balancing a boat.