[enneract]

Just have a look at what the author wrote!
See FAQ in the first post: "XBMCbuntu: Chrome does not start in fullscreen. What to do?"
Follow the link and read through the Chrome Launcher thread. You just need to start openbox with a custom script...

That does not work, unfortunately.

Works fine for me and several other users here. Looks like you are doing something wrong.
There are some example scripts available at the chrome launcher thread. Just adjust them for your needs.

I can't help that, all I can tell you is that it doesn't work. xdotool does not grab focus of the window, and, as nearly as I can tell, said script is not executing at all (replacing the script with a blank file still allows chrome to launch, which it should not, replacing the script with one which writes the arguments to a file and nothing else still allows chrome to launch and does not write said arguments to the file)