Facial Implants

I had Medpor mandibular implants placed about 8 years ago. My surgeon and I agree that the angles (lateral to the chin) are too wide for a female face, so he plans to trim them conservatively. I am 54 years old. He claims that doing this will not cause the skin to sag, giving me jowls, which I really, really don't want. He says the skin will shrink, especially since he is trimming just a few millimeters. Is that right?  I'd rather have a wide jaw than jowls. Would you please advise before I proceed? Thank you, Dr. Garcia.