I have one in each door cup holder.
one in rear Driverside corner secured.
Warning: The doors. keep tabs on that pull tab!!!. Mine fell out, Girl friend went to do something her foot triggered the Extinguisher. While I was doing 55+ When Cloud Enveloped Cab!.. Talk about Emergency Evac stop and venting. what a MESS!!!!
I have a 5-BC in the little passenger side bay in the back. Screwed the mount that comes with the extinguisher to the top angled part and the can is a perfect fit. Not my pic, but very similar to this: