Neither of those tactics work on my boat. from 0 to 10 knots or so, I can sail to windward nicely without any board down, above 10 knots, I'll begin to lower the board in increments to help reduces weather helm and leeway, and allow me to point higher...I've been playing with just how much..but, halfway feels right between 10 and 15..above 15 I'd probably lower it completely.
Off the wind, the board starts coming up in increments until when downwind there's no board down.
Thatís been my experience as well.
Also, on a reach in heavier air, we tend to add a little more centerboard to help keep us from slipping sideways, and trim the sails for balance.
Lowering the centerboard in a moderate chop helps stabilize the boat. It stands to reason that if the boat is better stabilized, airflow over the sails will be improved.
I donít think there are any hard and fast rules for centerboard use, just rules of thumb. Your boat will tell you what she needs, you just have to listen to her. But kind of like my wife, knowing exactly what she wants takes some practice and experience.