From your photo an incision on the areola would probably be best. As for the size, I usually ask people to perform the rice test to see what size they would be most comfortable with. If you are not confident with your measured breast width you can always ask your plastic surgeon to visually check by using a sample implant and put it up to the breast and see if the edges of the implant are wider than your breast. Also, you should carefully consider what stye of implant you will receive. Below is a link to how to do the rice test.
Dr. Wali’s office is located in Claremont, CA serving the greater Los Angeles, Inland Empire and Orange County areas.