In the on going saga of buying my first C16, one that has been on the trailer for several years and has experienced a leaking cabin roof, water in the keel and a subsequent alteration from concrerte to a soil balast in the keel, I too have followed the problem of how to improve light air performance. Rounding the bottom of the stub keel to a hydrodynamic profile was my previous suggestion.
The first great improvement to the C16 was the foil rudder. I see evolution through the Legacy, some modifications of which include more sail area foward which also lessons the weather helm.
Last night I sketched modifications to the main sail, trying to get more area. It seemed that a gaft would do a good job of increasing the gas pedal without raisng the center of effort very much. Each time I did the sketch I raised the peak of the gaft which raised the center of effort and moved the center of effort foward. Eureka! Has anyone made a light air (nylon sail) sliding gunter for a C16? This modification should be easier to accomplish than mounting a taller mast with new sails with its unintended additional strain on the rig should one not reef early.
My inspiration was post #13 by Capt Nemo from "Has anyone taken the Brakes off?" which see. There is a great photo.