Thanks to all who responded to my earlier posting about a skeg on a G17. Built a mockup of 1/2" CDX, a triangular fin about 9" x 4-1/2", hot glued it between Forms 13 and 14. It was blowing 20 kts. today, and she tracked straight as an arrow at all points of wind, so that seems to be the answer. I'll be back after I debug the trunk and controls.