Does Ultherapy work just as well in isolated locations on the face as it does all over the face?

I am looking into ultherapy for my jawline and chin at age 35 for early skin laxity in these areas. I have a genetic disposition to jowling and developing loose skin under the chin worsened by chin recession. Would opting for ultherapy just in these zones be just as effective as doing the entire lower 2/3's of the face? Or does the treatment work best when a large area is covered at once?