I'd recommend expanding the browser configuration information on your site to include the options found under about:config.

There's a bunch of settings in there not available under the main settings. Eg privacy.resistFingerprinting -- which actually has a bug where your browser suddenly stops opening full screen, even with this setting disabled. Solution is to toggle this setting on and off, restarting browser between toggles, and Firefox will remember to open full screen again next time if that's how you left it.