A past discussion asked if a masthead-rigged mast could be bent aft to trim a mainsail. I just have run across a chapter in "Understanding Rigs and Rigging" by Richard Henderson that addresses the question. The short answer is maybe as it depends on the design of the masthead as well as the rigging. Simply put: If extended lines are drawn above the mast of the forestay and backstay and they meet on the centerline of the mast, the mast will not bend. If the backstay crane is lengthened the extended lines will now meet aft of the mast centerline creating a "bending moment" allowing the mast to be bent aft. A bluewater cruiser would probably want the added strength of a straight mast and lose a little sail trim. The racer would want the best possible sail trim and lose a little strength.