Rivered backdoor flush on 4 flush board - line check 100nl

[mdm13]

Villain is 30/10/1 over 400-450 hands with street by street AF, of 1/1.5/4 WTSD of 29. Has peeled flop superlight in the past and has folded to second barrels a few times. Bluffed a missed draw once, and stacked off with an overpair in a bad spot I think. Comments on all streets welcome. Cbet was suppsoed to be 7 btw. FWIW, I checked the river fairly quickly.

Full Tilt No-Limit Hold'em, $1 BB (6 handed) Full Tilt Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

MP ($69.80)
CO ($215)
Button ($101.70)
Hero ($100.50)
BB ($100)
UTG ($119.15)

Preflop: Hero is SB with A[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/spade.gif[/img].
<font color="#666666">2 folds</font>, CO calls $1, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $4.5</font>, <font color="#666666">1 fold</font>, CO calls $3.

Flop: ($9.50) T[img]/images/graemlins/spade.gif[/img], 3[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $6</font>, CO calls $6.

Turn: ($21.50) K[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $12</font>, CO calls $12.

River: ($45.50) 3[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets $29.5</font>, Hero calls $29.50.