Force Citrix Sessions Full Screen

The Citrix Receiver remembers the windows settings and size for each connection.

These are stored in
HKCU\Software\Citrix\Xendesktop\DesktopViewer\{resourcename}

If you want to override all of the individual settings and for example force full screen each time you can set the following key in the Root

ForceFullScreen  REG_DWORD = 1