seandwyer wrote:So, how exactly do you use the topping lift to adjust the sails? I'm interested in this.
When the air is really light, the boom may flatten the sail excessively simply by weight. Nudging up on the topping lift can allow the sail to assume a better shape (for upwind). This is an issue in those situations where the wind is not strong enough to shape the sail and where you need to use other tricks to cause the sail to be in the correct shape, so that any airflow that hits the sail can produce lift. Another common trick is to heel the boat to leeward so that the sails will not hang straight, but form a curve to leeward, as usually.
That's different from what you see Lasers do on light wind runs, where they heel to windward to get more of the sail area higher up (where laminar air flow is faster).
The DS boom is heavy enough that using a TL in those conditions should be effective, but while I'm familiar with this technique, I haven't tried it on my DS (don't have a TL installed there yet).