Great mod - I created a plugin to do something similar but you have done well with this and it should have been standard for vb4 - well done Mate!
There is always a BUT

... as I will have different pages in the sub menu of a tab, the only problem with the new vb4 tab menu system is that a user has to click a tab first before they can see the sub menu items - not your fault mate but rather a vb fault with lack of forethought in making their navbar more user friendly in my opinion.
It would really enhance this mod if there was some way that on-hover of a tab changes the sub menu items to the ones under that tab you are hovering on - helps the user to decide if that tab has the sub menu items they may be looking for - when the mouse leaves the navbar hover the sub menu items are back displaying the items for the selected tab.
Just a thought but would be greatly helpful to site users