Nut flush draw on a paired board

(This was on ParadisePoker, don't know how to upload hand history)

I have A[img]/images/graemlins/diamond.gif[/img] 5[img]/images/graemlins/diamond.gif[/img] on the button. MP-1 calls, MP-2 calls, I call , SB calls, BB checks. 5-way to flop.

Flop comes Q[img]/images/graemlins/diamond.gif[/img] Q [img]/images/graemlins/club.gif[/img]4 [img]/images/graemlins/diamond.gif[/img], checked to me, I check for a free card.

Turn shows Q[img]/images/graemlins/diamond.gif[/img] Q[img]/images/graemlins/club.gif[/img] 4[img]/images/graemlins/diamond.gif[/img] 5[img]/images/graemlins/spade.gif[/img], SB bets, BB folds, MP-1 calls, MP-2 folds, I call.

I feel like checking the flop was the correct play. If you disagree, let me know.

Is the turn bet worth calling? It's a $9 pot, and if I hit my [img]/images/graemlins/diamond.gif[/img] flush, I figure it won't build too much more on the river. If someone else has two lower [img]/images/graemlins/diamond.gif[/img]'s, I might bank if a [img]/images/graemlins/diamond.gif[/img] does hit, but that would reduce my outs from 9 to 7. If one of these guys is slowplaying a Q, he might hit his boat on the river or already have it. I figure it unlikely enough that this isn't the case so I call.