go with what mr traynor suggests hun.honestly just because ur friend started the same etc means nothing.
me and my sis in law were both an AA cup,i was a 32AA and she was a 34AA, we both had 380 under muscle, she is a 34FF and im a 32F however we look completely different.
go with 415/450 as the naturelle rang are different sizes to the cui (which ur friends 380 prob were)
xxx