The hitbox for TFU is alot smaller than the playermodel due to the TFU clothing being around 75% thicker than the actual hitbox. Maybe if they made the hitbox bigger, TFU wouldnt be impossible for new players to kill.
However, as much as it pains me to say it, the solid fact is NOTHING will be done about this. TFU will stay how it is and we're all gonna have to either pack up and play somewhere else or just live with it.