You seem to know the guy pretty well for only being about 6 or 7 hands in. I take it you play with him often.

I make these types of plays PF all the time . . . but only when I have solid reads both ahead and behind me and can lock up position.

Here's what I don't understand: if you're in MP, how are there only 2 loose passives behind you?? That would mean you're on the button. If you're in MP, I'd expect there's at least 4 players left to act behind you (CO, Button, SB, BB). Now unless you play with these guys all the time, that's too many players to have to wade through with virtually no reads with 78s. So I fold this hand unless I'm at least the CO, but more likely the button.

So here's what I'm thinking: if you're intent on making this play against a loose aggressive player with so many players left to act, then don't screw around and just passively call. Take control of the table by reraising to lock yourself in position and put the pressure back on your opponent. You can now win this one three ways: You can outflop your opponent, you can outplay your opponent after the flop (you've represented a big pair or AK here), or you can get him to fold PF. And the pressure to make a decision is back on your opponent, who likely pitches the 55 down to any sizeable reraise.

If he comes back over the top, then you made a bad read and it's time to take your medicine and get out of the hand. If a player behind you comes over the top or just flat calls, you're in big friggin' trouble - run for your life (then remember the value of position next time).

But my advice is to just fold in this position with so little information about the other players.