Hi i’ve not had the surgery but i’ve been for my consultation and have my date booked, and I thought I would be recommended under’s due to only being a small A cup now (not completely flat that being said) but the surgeon actually said for me he’d opt for overs, because I have enough breast tissue, and his assistant mentioned there is often less complications with them moving with overs when pregnancy etc comes into it because the muscles change. I think if you are very flat they recommend unders because otherwise the implant may be more noticeable. Either way, I think you may be able to have a say in it if you want, but really you should go with what the surgeon feels is right for you and your frame.
Hope this helps 🙂