50NL 6m 99 overpair turn decision

[nogenius]

PokerStars No-Limit Hold'em, $0.50 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Button ($44.45)
SB ($65)
BB ($80.30)
Hero ($51.10)
MP ($49.25)
CO ($37.60)

Preflop: Hero is UTG with 9[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/spade.gif[/img].
<font color="#CC3333">Hero raises to $2</font>, <font color="#666666">2 folds</font>, Button calls $2, <font color="#666666">2 folds</font>.

Flop: ($4.75) 4[img]/images/graemlins/heart.gif[/img], 2[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $3.5</font>, Button calls $3.50.

Turn: ($11.75) 5[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero ???</font>

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Villian is an unknown.

My usual line here is to bet 2/3rd on turn, then check/call almost any non-heart river.

What's your usual line here vs. an unknown?