Villain is about 50/40 with 20% 3-bet. Very aggressive post-flop, no showdowns in big pots yet.

Thoughts on 4-betting vs. flatting here?

Full Tilt No-Limit Hold'em, $0.50 BB (2 handed) - Full Tilt Converter Tool from FlopTurnRiver.com

BB ($159.20)
Hero (SB) ($126.45)

Preflop: Hero is SB with 7, 7
Hero bets $1.50, BB calls $1

Flop: ($3.20) 7, 5, 9 (2 players)
BB bets $3, Hero calls $3

Turn: ($9.20) 2 (2 players)
BB bets $6.25, Hero raises to $15, BB raises to $30.50, Hero ???