The centerboard helps too!
Until recently, I didn't realize how much the centerboard on my water-ballasted boat helps the "righting moment". Seeing my rudder pop out of the water when it is released made me think (incorrectly) that the centerboard was fairly light as well. It was only when we pulled the centerboard to replace its broken line did we realize how heavy that sucker is. It takes two people to reasonably handle. With its long length and weight, I bet you mathematicians out there would calculate that the centerboard, in the down position, contributes a not insignificant amount in keeping the boat upright.