Indeed you are very small frame and band size.. but you are also tall, If I were I would go bigger, and trust me I don’t like having big boobs.. I just feel that 320 won’t be enough.. maybe try 320 on HP or 380 on UHP.. I’m 4’11, 32aa(so nothing really) and I’m going 300 (and I really don’t want big ones, just natural normal).. who knows I might be wrong..
But I’ve seen other woman saying that the sizers feel bigger than what they actually end up. The phrase “I regret I didn’t go bigger, as when I put the sizers on it felt good but now I’m post-op and they feel small” is common around the forums.
From the other hand you have very small band size body (around your bust), so maybe you can’t go bigger.. nothing wrong asking the doctor for a ‘push’ if possible and IF is safe of course.