clampbottom - Not sure what you mean by a "conginial curve." Do you mean congenital?
As I have said several times before and above, the data in the medical literature for effectiveness of an extender to straighten penis curves is sparse. It does work with after surgery to correct Peyronie's disease. When you surgically remove the plaque (hardened fiber mass) that causes the bend in true Peyronie's disease, the extender is used to pull the penis straight (at relatively low tensions) to allow it to heal strength. And a lot depends on how extensive the surgery.
The success of straightening curves with an extender is as variable as success in lengthening the penis with an extender. Straightening curves involves increasing the length of the short side of the curve. The success will always be dependent on effort. The key is stretch sensibly and understand it's going to take time - lots of time -- months to years. If you want it to work, stay motivated.
Good luck.






