light winds and older sails ...
There is a theory that having baggier sails in light air is better for two reasons. One, the baggier sails make for a less abrupt change in direction for the wind, so the moving air stays attached to the curved foil longer, and is thus more efficient. (Think of wind coming to a flat sheet of plywood - or a flat sail -- the flow becomes detached and turbulent, instead of being able to follow a gently curving route. ) Secondly, the baggier sails create more drive for cutting through light-air chop and slop. A newer, more finely tuned sail with less draft will be more efficient in smooth water and a steady breeze, but without those conditions, it may tend to stall out. Think of a jet fighter''s wing, with hardly any depth of chord (draft) in it. It has to be going 300 mph before it starts to fly. Then look at a DC3''s wing. It looks almost like a camel in comarison, but the DC3 starts to lift at closer to 60 mph. At slower wind and boat speeds, more draft is desirable. From here, however, we can''t tell what your sails actually look like, so it''s all just a guess. Try changing and see if it works. It may psych out the competition to have them think you''ve got a "secret weapon" in light air.