from "# If..." to "exit 0"

Your script should actually start with:
#!/bin/bash
# and insert any comments here, like what this script does

Then you want to name it such that you won't accidentally try to use it as a loginhook. My recommendation is "LogoutHook".

You can put the script practically anywhere, but try to think of a place that will be common for all such scripts going forward. We created a folder in the main Library folder for all custom scripting. That is where all of our admin level support staff can find them on any previous or future image builds.

You probably don't want read privileges for other, aka "world readable". After creating your script, from the command line, enter this and hit return:
chmod 770 /path/to/LogoutHook

You probably want to make root or "system" the owner, and maybe assign the admin group full access:
sudo chown root:admin /path/to/LogoutHook

I'm sure someone will correct me if I'm wrong on any of this, but it is working this way for my scripts.