river bluff induction?

villain is 40-25 over a decent sample, and pretty smart post-flop, I'm at two tables right now where he is 400+bb deep.
he's been steering clear of me postflop.
figure him for at least some sort of hand, and hope he picks me for AK, he knows I'm prepared to fold for stacks

Thoughts on river bet sizing?

Full Tilt No-Limit Hold'em, $0.50 BB (9 handed) Full-Tilt Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

SB ($53.10)
BB ($276.40)
Hero ($53.25)
UTG+1 ($97.25)
MP1 ($25)
MP2 ($50)
MP3 ($48.30)
CO ($10)
Button ($54.95)

Preflop: Hero is UTG with 8http://www.flopturnriver.com/phpBB2/...iles/heart.gif, 8http://www.flopturnriver.com/phpBB2/...miles/club.gif.
Hero raises to $1.75, 6 folds, BB calls $1.25.

Flop: ($3.75) 2http://www.flopturnriver.com/phpBB2/...iles/heart.gif, Thttp://www.flopturnriver.com/phpBB2/...miles/club.gif, Khttp://www.flopturnriver.com/phpBB2/...es/diamond.gif (3 players)
BB checks, Hero checks.

Turn: ($3.75) 2http://www.flopturnriver.com/phpBB2/...iles/spade.gif (3 players)
BB bets $2, Hero calls $2.

River: ($7.75) 8http://www.flopturnriver.com/phpBB2/...es/diamond.gif (3 players)
BB checks, Hero bets $6.5,