Interesting
David, I have a DS II, but I think the DS II and DS III have basically the same centerboard control line rigging. The down line on your boat might be stretching or the knot slipping on the cleat. Do you have a traditional "horned" cleat to secure the CB lines, or did Pearson (yes, Pearson was the builder of the DS III from late 1989-91) use a "clam-cleat" on the CB lines? A clam-cleat looks like a slotted fitting with teeth i nthe slot to grab the line and hold it, plastic clam-cleats can wear out after a while (a few times of having the cb hit bottom will do a number on the line and cleat) also the line wears out a bit and is harder for the cleat to grip.My Cb will stay down pretty well, but I have a horned cleat and tie the board down when sailing (loosely if near shallow water). Even with the board not tied down, mine will not ride up too far, and will usually drop back down as I tack.