when to slow down with a queen overpair

[mosch]

Party Poker 3/6 Hold'em (10 handed)

Preflop: Hero is MP2 with Q[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/club.gif[/img].
UTG folds, UTG+1 folds, UTG+2 folds, MP1 folds, <font color="CC3333">Hero raises</font>, <font color="CC3333">MP3 3-bets</font>, CO folds, Button folds, SB folds, BB calls, Hero calls.

Flop: (9.33 SB) 6[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/club.gif[/img], 8[img]/images/graemlins/heart.gif[/img] <font color="blue">(3 players) </font>
BB checks, <font color="CC3333">Hero bets</font>, <font color="CC3333">MP3 raises</font>, BB calls, Hero...

[Alobar]

I 3 bet. if he caps or pops me again on the turn, then I call down