Tongue stretching and extension surgery?

Do you mean having your web cut? That might add some length, but it might not, and you'd probably have to search hard for a body mod professional willing to do it, and you'd need one that's very experienced and that's confident that you don't have an excess of blood vessels that would make it overly risky. I doubt you'll find an actual doctor willing to do it. Most surgeons will only cut a tongue web if your web is large or your tongue is short, so if your web doesn't stick between your bottom front teeth when you stick out your tongue, they won't find it necessary.