Question: Sail seems very flat what am I doing wrong?
Answer: It's very difficult to tell what’s wrong without seeing it. Do you sail at a club with other Blazes? Obviously the best thing to do is compare with one that is right and adjust accordingly. Sails are very stable in shape for several years (none of your laser type stuff this!) and are fully competitive until they start falling apart eventually. Generally do not over tension the battens.
Make sure it has the right TAPERED battens are in it otherwise it will only work in a gale. Very little outhaul tension, only just enough cuningham to tidy up, and do not use kicker until you start being overpowered. Make sure rake is somewhere between 700 and 710cm, is 'sloppy' etc. Lastly check to see if the mainsheet attachments on the boom are directly above the opposite elements below - if they are too far back they will depower the sail under laod by shunting the mast forward.
Oh and yes do not sheet to the centre line unwind - the boat will stagger and be slow. You need to get the strop correct to ensure this cannot happen.
Best thing - get along to a training event or even the Nationals. You will know everything needed in a couple of hours then. So how old is the sail then?