10/20 limit, quick turn issue HU

[sy_or_bust]

SB is loose, and of average aggression, but defintely not a huge idiot.
MP2 is playing nearly every hand, and raising fairly often. (i.e. holds an A2 ~never).

Party Poker 10/20 Omaha Hi/Lo (9 handed) converter

Preflop: Hero is MP1 with T[img]/images/graemlins/club.gif[/img], 4[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/heart.gif[/img].
<font color="#666666">2 folds</font>, Hero calls, MP2 calls,<font color="#666666"> 3 folds</font>, SB completes, BB checks.

Flop: 3[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, BB checks, <font color="#CC3333">Hero bets</font>, MP2 folds, SB calls, BB folds.

Turn: 7[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, Hero...

So I'm wondering what SB peeled with that calls a turn bet, other than a 7 or 3. Maybe an overpair. I think he'll raise any full house, which is annoying. He would have lead the flop with A2, and probably raised preflop.

I decided to check, planning to raise a low card and call a high card. I was concerned about 1) getting raised and feeling forced to call down, 2) folding a hopeless hand that might bet the river. In retrospect this feels a little weak - I'm not sure. What do you think?