Step it up a little. Try to get it a little hotter with hot water, a hair dryer, or very careful use of a heat gun (my choice). Whatever you use, get it hot enough that you can barely, constantly hold on to it with your hand... keep checking it so you don't go too far. Move it slightly beyond where it needs to be (because it will spring back slightly) and block it there until it is completely cooled... on the INside... a couple hours. And then string it, work it, and see how you did.