Bob,
I had the same tracking troubles with my G L since launch in Jan. Somewhere I heard of this solution, also used by my friend Ron in Tacoma on his Guillemot.
I cut a piece of hardwood about 5/16" thick into a long taper 24" long, 3/4" at wide end and tapers down to nothing. Hot glue it to your stern so that the wide end is about where the stern really starts to rise. If it doesn't do the trick it's easy enough to make it wider or longer or both. It tamed my G L so nicely I popped it off and glued it on permanently, it was a piece of Honduran Mahogany and matched pretty good for color so I just cleaned it up and epoxied it in place. Don't have any weathercocking problems and this could be a whole different ball game. (Go M's)
Ray