I am a little bit cautious with the flash backup approach, When my original 2400 master failed, I replaced it with a just decommissioned 2400 thinking I would be up an running within minutes.
I though the Flash restore would be a simple procedure but encountered issues with licensing, missing policies an other changed items. It was possible that the flash backup from the original master was corrupt since it was taken just days before.
The information all appeared in the Flash backup file, and it was used to rebuild the master in a matter of hours.
I am not under the same pressure to get up and running and the lab test does sound like the way to go before going live.