I Am Getting a Terino Square Chin Style 2 Implant..but What Size? (photo)

Although this opinion is incomplete without an examination, I would tend to agree with your Plastic Surgeon.  I think that a large implant would produce an aesthetically pleasing result, while an extra large is probably too big.

 In our experience, the size, the thickness, and the shape of the chin implant is determined at the time of the consultation and examination. It's important that you do not want to look surgical, and look like  you had a chin implant, or have complications from such a large implant being placed.  In addition, a properly performed neck lift will accentuate the chin area along with the implant.  See the link below for examples of neck lift and chin implant

If good lateral dissection is done back to near the jaw angle area, there will be no risk of the central square part of the implant folding upon itself. Unlike many more typical chin implants, one has to know that very complete dissection must be carried out along the jawline to make sure the implant settles evenly and easily onto the chin area.