Hi, Piro!
The only drawback I know about 'Tabs On Bottom', persistent and never fixed IMO,
is the reactivation of the title bar I deactivated via the customization menu…
=> Thank you already, and in advance perhaps, too! I still enjoy this XUL App <3
Context of the report:
• Firefox: version 44 and below, with its default theme;
• Firefox extensions: several (unlisted), but the I tried deactivating all the interface-related ones without success;
• Tabs On Bottom: version 0.7.1 and below, the 'bug' was always there (albeit invisible in fullscreen, of course);
• OS: Windows 7, 64-bit, with the default Aero theme enabled.
Keep up the very good job :-)