So, I went over the rules, and one thing came to mind... What about Tarutarus? They're naturally short, about three feet tall at most, when fully matured.
They're from the online game, Final Fantasy XI, and I'm sure this question has been asked before, but are they allowed? I know some might mistake them as young for their appearance, but the one I specifically have is around 20 and is physically and mentally mature, as much as Tarutaru can get, just... Really short.