It was time to replace the original Halon horizontal Fireboy in the engine room on my 1994 390CPMY. However, no more halon, so it is some FK-5-1-12. It is longer and heavier, so there is no way it will fit against the forward bulkhead horizontally. It does say mouth vertically anyway. I have room in front to the port engine (454 Gas) that will allow it to go vertically. However, it would need to go into the outer stringer. I know they are all fiberglass. I was thinking of a 3/4” PT plywood, with 5200 behind it to anchor it against the stringer. It would be mounted right where the documentation number plate is in photo 2. Then use lag bolts to go through the plywood and stringer. Thoughts? Advice?