i,ve been windsurfing about 10 times and i love it.At this stage i,m able to sail back and fourth at a bit of speed ,slowly turn around and have also managed a coulpa beach starts,all this done on a board which is huge,i suspect 330lt . It takes it out of me hanging on to the boom for any more than an hour.Question is should i at this stage start to use a harness or move on to a smaller board ,which i,ve already got(140lt bic blast).Try and get to this level on the bic and then go the harness .The big board has no foot straps,so i guess i have to skip that part if i stay on the big board any advice will help cheers
There is no defined time or stage when to start using a harness. That is up to you. As to what board you should be on while learning a harness, I would say the most durable one. The reason is you'll be getting more into the catapult stage where people have a tendency to destroy the nose of their board (if it isn't a poly board). Generally the rig may throw you in a gust and the boom/mast ends up hitting the nose of the board.
As soon as you a sailing back and fro get in the harness. You can't sail without one so you may as well get used to it asap. I had my GF start using the harness second time out. Now she is quite comfortable with it and working on her planing technique in harness. Moreover it will make your sailing more enjoyable and give you more time on the water. 
Persevere for a bit longer bighen ,and master the basics befor you get in to the harness,see how you go on your 140 lt as well ,there is no real rush,its quite amazing rearlly the length of time as a beginner you can sail without a harness,,once you feel competent in your abillity to control the wonderful feeling of the wind driving you forward and leaning back on the sail in control then you will be ready to move on to the next level of getting in to the harness,then there is no turning back ,stay with it.
