What is the best method to reduce a vertically long chin and give it a v-line shape?

With chin reduction surgery, you may need both a vertical reduction and then a chin "tuck" beneath the chin to prevent droopy soft tissue. The key is to maintain a natural mentolabial fold.

A t-osteotomy is sometimes helpful, but if you have excess skin it can sag more. We do 3-4 jaw surgeries like this a week, and pictures or a video are the next step for good guidance for you.

By definition when a soft tissue chin pad sags exists with a vertically longer chin bone, any form of intraoral bone reshaping is going to exaggerate the soft tissue problem. Thus a submental chin reduction where both bone and soft tissue can be reduced at the same time would be the preferred approach