Hi!
I have no personal experience of this, but multiple sources online seem to cite 5'2" as the preferred shortest height for driving roles, although this seems to be a guide and it ultimately comes down to, as you say, your ability to operate the controls safely.
However (and this is pure speculation), it is likely that trainees at Avanti will be learning the new Hitachi sets and, being that they are a product of the modern era, I'd have thought it highly likely that the cab ergonomics are designed around a very wide demographic of people.
Perhaps any 390 drivers can also weigh in on their experiences in this regard?
I wish you the best of luck with your application!