messy code or a messy page? i say do what you like as long as those with eyes can see the nav and it still allows people to tab through the nav.
not quite sure what the hell you're trying to do with the scroll bars. surely 'to appear when required' is the answer - or do you want people to scroll left and right to nothingness? i say its a dangerous area to get into anyway. its one thing to change page navigation but when you start playing with how the browser actually functions you have to ask yourself if you're using a medium for something that its not meant for?