I do repeated heat treating on white woods with a heat gun. Just one good time with yellow woods. I don't go by temperature. When the bow's back gets hot to the touch all along the limb I stop. It has worked for me so far, but may not be the proper way, so take it with a grain of salt. Badger , and Mark, and some others could help you out to do it the right way. I did it one time just to see how it worked for me with Hickory, and not concerned about the back breaking, and it didn't . I have been doing it that way ever since. When you fire harden a bow the back gets very hot. I have done 5 with the fire harden method, and no breaks yet, but I haven't shot thousands of shots out of any of the bows yet. In the long run I am not sure what will happen. You are tight with the Badger who makes world record flight bows, and Mark who sort of wrote the book on heat treating. No better sources that I can think of.