I have not performed much, except in choir & as a teacher. My advice, as in most things, is to maintain a sense of balance & do what feels right to you. One possible pitfall of eye contact was humorously covered on the Allie McBeal Show recently. A performer sang "to" an audience member in way that was perceived as so intimate that she left her husband for the performer! Watch out for that one (unless it's what you had in mind)!

best,

bbc