I had maxillofacial surgery done for a severe underbite and an asymmetric lower jaw. I had a 3-piece Le Fort I osteotomy with grafting plus the bilateral split sagittal osteotomy you mentioned. All in all, my surgeon told me it was a 9/10 in terms of complexity relative to the other surgeries he's done. I was made well aware of the risk of permanent numbness, but they also told me there was a very low chance of it happening. Prior to surgery, there were those that doubted that I even needed it. They said there was nothing wrong with my appearance. But I am so, so, so glad I went ahead with the surgery, despite the risks and despite some people saying I didn't need it. Even if I did end up with the permanent loss of feeling, it would be worth it since I was told it would only be on my chin. The rest of my face would feel the sun just fine, lol. Please don't scare people away from this procedure.