Ubuntu technical problems and solutions reference, a modern cookbook.
Because Guake is not yet Unity ready, the lower right corner of the terminal is not visible, hence you can not drag it to re-size the width.
Because there is no option for setting the width, the solution is to edit the python script, and manually set the desired init width. As soon as the lower right corner is visible, you can re-size with the mouse as much as you like.
Because you need to be root to edit this script, run:
gksu gedit /usr/lib/guake/guake.py
Then, go line 817 (that’s valid for Ubuntu 11.10 at least), where you see the following code:
screen = self.window.get_screen() height = self.client.get_int(KEY('/general/window_height')) width = 80 halignment = self.client.get_int(KEY('/general/window_halignment'))
Here width=80 means the width of the starting window will be 80%. Set your desired window.
Thanks for the solution to Alin Andrei in his answer here