Dynamic Menu Cut-Off on Short Pages

I'm working on a dynamic products menu that has 3 levels and the 3rd level has a long list (~20) of categories for the user to select from. I'm not having any issues with the CSS Menu in terms of creating the necessary level and populating the categories from the DB but what I am having an issue with is the fact that if the page doesn't have enough content and the pages are relatively short, the menu doesn't have enough space to show the full list. Other than formatting the 3rd level to be smaller bars and attempt to cram things in that way, is there another option for the page to "know" it needs to be bigger to accomodate the expanded menu viewing?