command line installation

I am making a XUL application that must be installed via the command
line with no user interaction.  For development, I have made a .xpi
file and I install it manually (using the GUI) and my extension is
installed exactly where I want it:

C:\Program Files\Mozilla Firefox\chrome\MyApp\content\main.xul

I can launch the app at this location:

chrome://MyApp/content/main.xul

Which is exactly what I would expect.

I have been testing the installation of the exact same .xpi file on a
fresh firefox installation (where my .xpi was not previously manually
installed).  I use this command:

firefox.exe -install-global-extension MyApp.xpi

The command simply returns with no output at all.  However, the files
for my application are not installed in the location where I would
expect them and I cannot launch the application at the location that
works when it is installed manually.

Thanks for your help,
-m.