Well I went ahead and created a VBA macro to show, hide, and then toggle the reading pane. Then I added a shortcut to the toggle macro on the quick access toolbar. So that works as desired. Don't see a way to add a shortcut keyboard command to the macro as can be done in Excel for instance.
So if anyone knows of an easier way to do this, or if there is already a built-in command or shortcut let me know.
One aspect of this is that you have to deal with the macro security, and the program being Outlook, with spam e-mails always a threat, enabling all macros seems risky.