I am not an expert but I can just tell you from my windsurfing past, that the sail is made in such a way that when it is pulled down by the downhaul and pulled out at the clew the mast naturally bends. This preloads the top of the sail in particular and the rest of the sail generally and so that it maintains shape in stronger wind. ie. the sail flaps less. This makes it more efficient.

If on the other hand your mast is damaged or weak this may change things. What direction is the mast bent?