You will notice the mast responds by bending aft at the tip and forward in the middle from one to five inches, depending on how hard you pull. Heavy cunningham pressures twists open the upper leach and flattens the middle of the main by driving the luff forward. Now, pull the vang on hard without tensioning the cunningham. This combination will cause the center of the mast to bend aft from one to three inches. You can even increase this bend if you ease the mainsheet while heading down and hiking hard.
Mast rotation can also change the amount of bend.
The upper mast sections can be stiffened by using less rotation because the leach now pulls more on the stiffer fore and aft mast axis. Simply sliding all the boom blocks forward one to four inches will reduce rotation by the necessary five to ten degrees. Mast rake also has a slight effect on overall mast bend. Raking aft slightly will make the mast easier to bend sideways, and fore and aft for the same amount of main sheet tension. After becoming familiar with the mast from the forward position, the final view of the mast should be from the helmsman's normal steering position.