Be careful with old versions!
These versions are displayed for reference and testing purposes. You should always use the latest version of an add-on.
As user requested it now supports 1,2,3,4,5,6,7,8,9 and 0.
I stuck with ALT-4 as Fullscreen.
I also added a new quick way to customize the values, In the Menu Bar > Tools > ResizeIT
Thanks for your support, and sorry for the late update.
Keep on resizing!
I will try to deliver a new GUI that works hand in hand with Firefox 4.
In Firefox 4 you cant resize you 'Firefox main window' while Firefox addon dialog is shown.
* True Full-screen.
* Customize options.
* Added window position alternative.
* No need to restart Firefox for changes to take effect.
* And lots of tweaks and changes to the code.
Sorry for slacking off!