Mirrored body language is probably the most effective thing you could do to make the interviewer think you are like them. Sit how he sits, angle yourself the same, keep your posture similar, use the same tone of voice, volume, etc.
You're probably going to be hyperfocused on making yourself appear less feminine, but unless the other person know that you're trans, that isn't something they'll be taking note of. If they do, they're probably more likely thinking that you're a young, feminine gay guy than a trans person.