Your total combined weight is a big problem until the wind gets over 15knots. In air that light(5-7 knots) you need 180lbs or less on the boat. The downhaul should be on enough to remove all wrinkles in the luff of the main. You need to keep your weight forward of the main beam on all points of sail. Attach a bridle fly to the point where the bridles from the bow join the forestay. You need to know your apparent wind in these light conditions. Keep the telltales on your main and jib flying at all times-especially on the leeward side. If you do all of these things you should be doing significantly better in light air. You have the distinct advantage of caring about sailing more efficiently. A lot of people just go out to float around. You're bound to improve.