Sizing the valuebet of a backdoor straight flush

[kamel]

No reads as I'm new to the table.

PokerStars 50 NL Hold'em <font color="#0000FF">(5 handed)</font> HandRecorder v0.9b (http://www.dmasn.com/handrecorder)

Stacks &amp; Stats
MP ($57.90)
CO ($51.05)
BB ($69.95)
SB ($47.50)
Hero ($51.55)

Preflop: Hero is BU with 9/images/graemlins/spade.gif, J/images/graemlins/spade.gif
<font color="#666666">1 folds</font>, <font color="#FF0000">CO raises to $1.50</font>, Hero calls $1.50, SB calls $1.25, <font color="#666666">1 folds</font>.

Flop: ($5) 8/images/graemlins/spade.gif, J/images/graemlins/club.gif, 7/images/graemlins/diamond.gif <font color="#0000FF">(3 players)</font>
SB checks, <font color="#FF0000">CO bets $1.50</font>, Hero calls $1.50, SB folds.

Turn: ($8) Q/images/graemlins/spade.gif <font color="#0000FF">(2 players)</font>
<font color="#FF0000">CO bets $2.50</font>, Hero calls $2.50.

River: ($13) T/images/graemlins/spade.gif <font color="#0000FF">(2 players)</font>
CO checks, <font color="#FF0000">Hero bets what amount?

[Nogatsira]

First of all I reraise the flop for sure with TP.
I don't think you'll get much money out of the CO since he played it freaking passively, as if he has a weak ace or a very low pocketpair or something.
Bet $4 and hope he has something.

I bet potsize of river, hoping villain is holding a straight and calls your bet. He will fold most other hands anyway.

[CowsFTW]

A 9 only would make a straight and there are three cards to a flush. So you either get paid off if he has something or you don't. I don't see a reason to bet less than half the pot. I would bet $10~$13.

[kamel]

Well, Villain is unknown. On the flop, I have TPGK+Backdoor-Redraws. I think calling is fine, especially if I'd like to have the option for floating in future.
I would have to fold if he 3bets me on this flop and I really would like to see for at least the turn card in this hand.