I don't even prefer
Marvin! If there was a
Marvin in the family that I really wanted to honour - winner of a VC or the Grand National - and had a girl by mistake (!), I'd use
Marvin undiluted as a mn; as I would for a boy. Did you hear Marvina, or see it? Is it MARvinna or marVEEna? And I really don't think
Marva is an improvement.