I added some blocking and 1-by material for a mount to get everything plumbed up and get the box opening set to where it will be pretty close to flush with the finished drywall. It's pretty solid like this. (That wire poking through the drywall to the left of the vent line? That's the back side of the pantry where the previous owner half-assed the wiring of some power strips and a small, 2-breaker sub panel. That's all been deactivated and will be removed when I remodel the pantry)