Age requirement for butt implants w/ fat grafting?

I am 16 and have discussed this surgery with my mother who is on board but prefers for me to wait until my body is "fully developed", around what age is that? I'm really set on getting it done when I'm 19. I'm 5'4" and have been since 7th grade, and my weight stays between 120-130(almost always perfectly in the middle though) and I've maintained that weight since middle school as well. Will I be able to get 400-550cc round intro muscular butt implants? And what is the earliest/best age to do so?

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