You should also consider a "fireport", which is installed in the living compartment side of the bulkhead. Vetus and Marine
East both make fireports that have a plastic membrane that will split if pushed upon by the fire extinguisher nozzle. The benefit of this solution is that the plug won't come loose.
You should have a fireport between port and starboard engine rooms and the cabins in front of them. These are available from Defender:
East 6860 Fire Port - White Ring (approx $10 ea)
Vetus Fireport (approx $30 ea)
We have the Marine East on our Belize