ahh yes – I see what you mean, just checked the NFL 
what I would do is use animate – so kinda like…
Code:
var height = *calculate the height of the menu slide down box and store it in this var*
$("itemSelector").hover(function() {
$(‘boxSelector’).animate({top: height}, 500);
}, function() {
$(‘boxSelector’).animate({top: -height}, 500);
});
the hover function there will when you hover on, open the box, and then close it when you hover off… that is very rough to give you the idea.
Animate is actually the way I do pretty much all of my movement style jQuery effects as the slideDown/slideUp or whatever never work exactly as I want them to…
Here is some more for you to look at and see if it is right for you…