I use packing tape to tape the firewall to the pod after gluing. I have never had something break, even with a lot of stress on it.
The method that I use is shown in this video:
He calls it the main reinforcement tool because it really does provide a lot of strength. When the motor heats up the glue might melt, leaving this as the only thing keeping the firewall on. Some people use epoxy instead to fix this problem, but I have never had problems with hot glue melting anyways.