NL50: good river bluff?

[Smilin']

I only had around 35 hands on Villain, but seemed TAGish with maybe only moderate AG; nothing too out of the ordinary. I expected a fold on the turn. I think this river bluff is +EV given how I got there, but I wanted to check with you folks. How often am I walking into a trappy flush or boat? Is Villain likely to believe I have a flush given that I didn't take a free card on the turn? (Villain probably doesn't have much of a read on me.)

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.25/$0.50
6 players
Converter (http://www.neildewhurst.com/hand-converter)

Stack sizes:
UTG: $29.65
Hero: $38.45
CO: $33.40
Button: $49.75
SB: $51.90
BB: $37.25

Pre-flop: (6 players) Hero is UTG+1 with K/images/graemlins/club.gif Q/images/graemlins/spade.gif
<font color="#cc0000">UTG raises to $1</font>, Hero calls, CO calls, Button folds, SB calls, BB calls.

Flop: 2/images/graemlins/diamond.gif T/images/graemlins/diamond.gif J/images/graemlins/club.gif ($5, 5 players)
SB checks, BB checks, <font color="#cc0000">UTG bets $1.5</font>, Hero calls, 3 folds.

Turn: 4/images/graemlins/heart.gif ($8, 2 players)
UTG checks, <font color="#cc0000">Hero bets $5</font>, UTG calls.

River: 4/images/graemlins/diamond.gif ($18, 2 players)
<font color="#cc0000">UTG bets $4</font>, <font color="#cc0000">Hero raises all-in $30.95</font>,

[vixticator]

Don't shove. I think raise to $15 accomplishes the same. I think raising flop is better, you have position and a great draw with probably both overcards as outs. Good spot to double barrell. As played I take free card on turn. Definitely looks like a weak blocking bet but meh... don't need to go crazy here.

[creamfillin]

I wouldn't try to push anyone off an overpair or AJ and I can't imagine what else he has here. Had he made a strong bet on the flop I'm more likely to try something like this. Villain seems like a real donk judging by his bet sizing and I don't like making huge bluffs against them.