What if you try a hair dryer on the highest setting for a little longer? Holding it close to a stiff area for a couple minutes can make leather soft enough to bend. My winter boots had a hard back seam, and the hair dryer warmed it perfectly without any risk of burning the leather. A torch might work faster, but it is so easy to overheat and crack the material. With a hair dryer, you get a gentle, even heat that does the job safely.