Thank you for the responses. I realized (or, for you Brits, realiSed) that I should have also mentioned that in additon to using "up top" for "up ON [THE] top", my wife and her family also use it for "up AT THE top". For example, "The title of the essay is up top of the page". Again, I wonder if this peculiarity (well, it seems peculiar to my Colorado-based friends and me, at least!) is a common regionalism in Northern Virginia, where my wife was raised.