After some general rules of thumb about haw far forward or back to set my mast base. I normally set it as right back, with bigish race sails rake in the sail and head flat out down wind (who dosent like to go fast). this has its problem in getting back to the car sometimes especially in 25kt plus when I rig smaller. looking for a happy comprimise or some methodology in setting up.
There is no hard and fast rule as there is so many variables which come into play, there are some guidelines which help, but nothing goes past test and tune experimentation
Start with it in the middle and keep moving it back in 10mm increments untill you start tail dancing. At this point you have gone too far. kepp in mind the further back the mast base is you boom will seem higher.
Thats my 2cents. Using a gps will help with tuning
There are plenty of guidelines, but they all depend on what gear you're using, and what you're trying to do with it...
Almost all of the newer generation of shortboards will be happy with somewhere between 132 and 135cm from the tail.
Have a look at some of Cribby's stuff: www.guycribb.com/windsurfing_technique_holiday_DVD_0076v01.htm
Some people are firm believers in his methods (especially the harness line and boom height part), and others say it is complete crap, it's up to you to try it and decide for yourself!
The biggest problem is that it's all interrelated - change one thing, and you'll probably have to alter something else as well..
Elmo is right, tune, test, tune, test.. It's really the only way!
