Windsurfing mast position

Question
I recently bought a an 87 obrien windsurf board that I use on lake superior. I am still in the beginning stage and have not been able to get back into the footstraps. I noticed that the mast is adjustable from front to back and I thought this might have something to do with my problem.  Could you explain how positioning the mast differently will effect my riding?  Another question, is a harness important I do not have one or really know what they are used for.   Thanks For your Time

Answer
I must tell you that sailing a 30 year old board is not going to give you the best experience to windsurfing.  Those old boards were the hardest things to sail.  Not to mention that boards that old tend to absorb water making them heavy and even harder to sail.  Do yourself a favor and try to find a used board that is about 5 years old.  The mast track position is not the problem the board is the problem.  You will not believe how much easier and more fun the newer boards are to sail.  Normally on the old boards if you move the mast forward you will be able to sail upwind easier, if you move the mast back you will be able to sail downwind faster.  The newer boards are setup to keep the mast position in the same place because the newer sails are designed to compensate and adjust.  Harnesses are used to take the weight off your arms when you sail.  They are used in conjunction with harness lines; ropes that are tied or velcro attached to the boom.  Your harness has a hook and you catch the rope hanging off the boom and let your weight pull back with the harness instead of your hands bearing all the weight.  When you advance to high speed sailing it is an absolute necessity.