My surgeon recommended 300-375 for me to choose from. I’m 5”5, 30B, 53kg I preferred 325 when I was trying on but then did the rice test and I’ve decided to go 350cc as they look different when they’re in. I asked why he suggested overs for me as another surgeon has said unders. He explained for my body shape overs would look a lot better and more natural which is the look I’m going for. It’s also a lot less recovery time if you get overs apparently.
They choose what they think is best for you, if you’d prefer unders there’ll be a surgeon out there willing to do it as they all have different opinions of how your breasts are affected by the surgery.
Hope this helps xx