Is this turn bet big enough here?

[Haplo]

no real info on villains

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.25/$0.50
9 players
Converter

Pre-flop: (9 players) Hero is MP2 with 8[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/club.gif[/img]
3 folds, Hero calls, MP3 calls, 2 folds, SB calls, BB checks.

Flop: Q[img]/images/graemlins/spade.gif[/img] 4[img]/images/graemlins/diamond.gif[/img] 8[img]/images/graemlins/spade.gif[/img] ($2, 4 players)
SB checks, BB checks, <font color="#cc0000">Hero bets $1.5</font>, MP3 calls, SB folds, BB calls.

Turn: 5[img]/images/graemlins/diamond.gif[/img] ($6.5, 3 players)
BB checks, <font color="#cc0000">Hero bets $5</font>, ....

I'm asking this because I got two callers on the flop, and there is a flush draw on the board. Would a bet of 7 or 8 be too much on the turn--in case I get two callers again on the turn, which is quite possible. I don't want one of them to get good enough odds to call with a flush draw. Thanks.