Flat chest to A cup and still look and feel natural?

You really need to be examined and sized to determine this.Find a plastic surgeon with ELITE credentials who performs hundreds
of breast augmentations each year. Then look at the plastic surgeon's
website before and after photo galleries to get a sense of who can
deliver the results. Kenneth Hughes, MD Los Angeles, CA

I would recommend using 3 dimensional imaging to visualize what the implant sizes would look like in you. A picture is worth a thousand words. You may find that the implants look better in a different size than you expected.