I have a 10# Halon system in my car, plus a 1.25# Halon bottle in the interior behind my seat. Here's what the handle looks like:
I have the bottle mounted in the trunk, and plumbed to the interior, carburetors, and trunk (battery + fuel fill neck). The bottle takes up little usable space.
That is it to the left of the collapsible spare tire. I still have room for 2 folding chairs, tools, tonneau, and a folded up convertible top.
I reinforced my aluminum dash behind the handle, because I figured if I yanked that baby, I was gonna be pullin' it HARD!
I keep a safety pin in the bottle at car shows, just in case somebody decides to "try it out". Remember to remove the safety pin before driving or a track event.
regards,
Jeff