Highly suggest you do a dry run for a fire scenario. You'll quickly move the fire bottle as close to the driver seat as possible. This is a personal pet peeve and everyone is welcome to their own method, but rear mounted fire bottles really need to be rethought.
Imagine you are smelling smoke, someone yells that your Jeep is on fire, or if you are lucky, you see the flames first. Most likely not the case though as fires typically are near your t-case or engine bay.
So, your Jeep is on fire.
1. If on grass or brush, drive to an open area. Putting out your Jeep is one thing, putting out the brush or grass that could inevitably burn your Jeep down is another. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
2. Put Jeep in park. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
3. Turn off Jeep. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
4. Unbuckle seat belt. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
5. Open door. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
6. Climb out. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
7. Accessing rear mounted fire bottle: open rear door and reach around rear bench, open tail gate, lift hardtop lid, or lift / unzip soft top window. Fumble with soft sided mount or pull metal pin from mount. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
8. Locate source of flames. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
9. Pull pin. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
10. Aim bottle away from you. (9 or 10 are interchangeable depending on your adrenaline and panic level). (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)
11. Fight fire. (YOUR ADRENALINE AND PANIC LEVELS ARE UNHEARD OF)