350cc, moderate BA for small chest inverted triangle body shape, will I look unbalanced?

It's very difficult to answer your question without frontal photos or an examination. Many surgeons have sample implants that you can "try on". This will give you an idea of how you may look after surgery and can assist you in determining if you feel unbalanced with them.

Please post frontal, oblique and side view photos of your breasts to allow me to give you an accurate assessment.

Without an examination in person it is difficult to comment. Your implant selection may or may not be a good one. Breast and chest measurements, breast laxity, and the “look” you are hoping to achieve (“natural, proportionate” versus “augmented” or exaggerated upper pole fullness) are key in determining which implant(s) are suitable.

For input from us in this forum we would need to see photos of your breasts and body from the front. Since you already have a plastic surgeon please direct your questions to him or her. In my own practice, patient input is key with regard to “the look” my patients want, but I do not delegate implant selection to my patients. I take on the responsibility of implant selection with the expectation that my judgment and experience will result in a beautiful result and a happy patient.

Please discuss your concerns with your plastic surgeon. Best of luck to you.