From my experience sailing sportsboats with gennekers, comments on the Weta forums and limited experience wih my Weta, it would seem that the rule of thumb is:
– Go for speed by turning up in the lulls and down in the gusts. Faster and further is better than lower and slower.
– If overpowered always head downwind – don’t luff up (you’ll likely capsize)
– If it’s windy, hoist when heading more downwind and then point up to your course
– Don’t cleat the gennker (you can’t anyway in the standard setup) and adjust it as you turn up and bear away to keep the top trailing edge so it’s just starting to break (harder to see if you don’t have clear sails).
Your aim is to get to the leward mark as fast as possible but this is a trade off between distance sailed and speed which can be expressed as Velocity Made Good or VMG. While you’re not allowed to use electronic instruments in Weta Class racing (Hurumph!) there’s nothing to stop you using them in open races or in practice – and use VMG to give you an idea of what the best heading is for a given wind speed.
You can get expensive marine instruments to do this, but a cheaper solution is to get an app called iRegatta ($9 for iPhone or Android) and a waterproof case or armband depending on your phone/tablet. iRegatta displays most of the functions of dedicated kit including VMG. More here http://www.letscreate.dk/letscreate/?q=node/1