I use to wonder if there is any way to streach the skin under the chin. I've noticed that on men with slightly saggy chins, the apple doesn't show.
If you could pull the skin out a bit and hold it with something that is very gentle, it might eventually streach.
But you would have to be really careful that anything you used, didn't pinch the skin too much, or you'll get really sore, or even cause some permanent tissue damage.