NIce! Rated 4 out of 5 stars

Very Nice.
I hope this works with Tabs in Titlebar userstyle like http://userstyles.org/styles/42402 .

This review is for a previous version of the add-on (1). 

Were you able to check if it worked with that Tabs in Titlebar? I would assume it behaves similarly to a normal maximized window with tabs in the titlebar.