Does a chin implant that gives projection also give an increase in vertical length?

Only one special type of preformed chin implant adds vertical length as well as horizontal projection, the vertical lengthening chin implant. It brings the chin down as it comes forward in equal measured amounts. (45 degree angulation)

 Hi, I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.  Non smiling photos of your face from the front and side would help in the evaluation.  When the chin is weak, this creates an imbalance making the nose appear larger, the mid face top heavy, the lower face looks short, de-emphasizes the lips and allows early formation of a "double chin".  
 Proper placement of a silastic chin implant adds forward projection to the chin thereby creating harmony and balance to the lower face.  Using the same incision, liposuction can be performed to reduce the fat and further shape the neck.  Excess skin, from below the chin, can also be removed through the same incision.  
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty (requires extensive tissue dissection, bone cuts and placement of metal screws and plates to secure the cut segments of bone).  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.   There are many different shapes and sizes of chin implants.  In my experience there is rarely a "true" lack of vertical length of the lower third of the face however, this can easily be assessed with a non smiling front view of your face.  
Hope this helps.