It depends on one simple tool
Hi Rich,You need a GPS then pick a waypoint about 2 miles or so directly down wind. To determine fastest point of sail - change heading and sail trim until VMG (velocity made good)is maximized.Same is true on any point of wind. The more off the wind - the faster the boat will go. The more off the wind - further to the mark. GPS VMG display show optimum. Oh how simple technology makes things.Good luck,Bob