Rated 4 out of 5 stars
Just by installing this theme, I can get TB11 menu bar back to the top maintaining the mail bar inside the tabs.
Still, I would prefer to keep the Aero style buttons instead of going back to TB3 style buttons.
Feel free to install another theme then, that's what the whole theme-thing was made for - every user selects the theme he likes the most ;)
Note that as you already pointed out in another rating there are userchrome hacks to archive what you want - without a theme change.
For others: he referred to https://getsatisfaction.com/mozilla_messaging/topics/anyway_to_put_tabs_under_the_main_menu_bar_in_new_version