I was just watching my DVD of the 85 French Open final between Evert and Navratilova and was really struck by how flat Evert hit her strokes. Though there were women who employed head topspin and moonballs (Jaeger, for instance), Evert hit fairly flat off both wings, and yet she has the record for most French Open titles. It makes for an interesting contrast with the men of the time. The players who were successful on clay in the 70s and 80s (Borg, Vilas, Wilander and Lendl) all hit with a lot of topspin. I've seen videos of Borg vs. Vilas, and the two practically hit moonballs the entire match. The same can be said of some of the Lendl vs. Wilander matches I've seen.