10NL fr: AK doesn't connect. bluff river?

[gedanken]

UTG+1 is 44/1/.6
CO is 26/8/6

PokerStars No-Limit Hold'em, $0.10 BB (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

UTG ($7.20)
UTG+1 ($6.30)
Hero ($19.85)
MP2 ($11.35)
MP3 ($12.95)
CO ($7.15)
Button ($29.65)
SB ($14.60)
BB ($19.95)

Preflop: Hero is MP1 with K[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/spade.gif[/img].
<font color="#666666">1 fold</font>, UTG+1 calls $0.10, <font color="#CC3333">Hero raises to $0.5</font>, <font color="#666666">2 folds</font>, CO calls $0.50, <font color="#666666">3 folds</font>, UTG+1 calls $0.40.

Flop: ($1.65) 8[img]/images/graemlins/diamond.gif[/img], 7[img]/images/graemlins/club.gif[/img], Q[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
UTG+1 checks, <font color="#CC3333">Hero bets $1</font>, CO folds, UTG+1 calls $1.

Turn: ($3.65) 9[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
UTG+1 checks, Hero checks.

River: ($3.65) 7[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
UTG+1 checks, <font color="#CC3333">Hero ???</font>


my cbet is a little light here, I see now. I normally aim for 2/3 to 3/4 pot. no explanation.

villian doesn't seem very imaginative, so after his river check I'm thinking he might let go to any bet. If I try it, how big? I'm obviously folding to any raise.