Tack as you reach the top of a wave. Place weight at back of boat to move less water. Let 12 inches of mainsheet out as you come eye to wind to allow mast to swivel and boat to complete tack. Move across as late as you can so wind pushes bows, which are high and clear of water across and head down of wind to get speed before pulling main in.
If you do not let main out you will not go across heavy wind with a wing mast.