Like others, I’d estimate I’ve cut my curvature in half since I started PE. I also tried an extender,and found it to be useless.
What I tried was a variety of techniques to put the most stress on the “short” side of my penis. I didn’t use a scientific approach, so I can’t say which one is best.
In addition to the exercises descibed earlier, you might also try a v-stretch or an inverted v-stretch. You might also try hanging with a fulcrum or twisting your penis as you hang.
If you choose to try the hanging approach, start with light weight and short time periods to see how well you tolerate it. And as always, you should warm up first so the ligaments and tendons will stretch more easily.