What Level at What Part in Thunderspire Labyrinth

[SlyFlourish]

I'm running my group through Thunderspire Labyrinth and I want to make sure my level pacing is right. At what points in the adventure should my party hit level 5, level 6, and, if they're supposed to, level 7?

 

[BlueBlackRed]

My group isn't that far into it at the moment, and they're all varying levels thanks to attendance.

But I would guess that they start around mid 4th (average level for the group), then be 5th by the time they start the duergar section.

Beyond that I've not read enough to give an answer.