Aaron Kernan is best suited to an attacking half back on a dominant team. This way he can overlap and as his teammates have faith in him, he will get plenty of ball and use it well. Half back suits him because it means he is generally playing against someone who doesn't want to tackle back. He has not worked out at half forward for probably several reasons but one is that he is being marked by someone who sees their job as marking him so he isn't getting the latitude he would get from a reluctant wing half forward.