I assume you mean upwind, since you hooked the sail:

Sorry to keep beating the Bethwaite drum here in the land of Smyth and White, especially since he's a Skiff (not Cat) sailor, but his flat water light air advice for Cats is to forget about the bottom 2/3 of the sail, as the only significant wind is aloft <5kts. Use a mast head balanced feather (or mast head streamer) to reveal the apparent wind aloft, maintain the upper sail 20 degrees to this apparent wind at all times, even if the skipper has to hand-hold the boom instead of using the sheet. Foot off to get some "reasonable" speed, and then head up as high as you can maintain this speed, footing immediately at any sign of lost power, and continually maintaining upper sail trim. Keep powered and keep moving, because if you stall the top of the sail it will take a long time at these wind speeds to recover (long enough for wind to pass 6 times across the sail front-to-pack). He says the boats that keep moving always win, even if much of that movement is cross wind.