unfortunately, no, there's no way to make the Notification Center go all the way to the bottom of the screen (unless, of course, you have a bunch of notifications or NC tweaks ... or both).
The fact that I find the Notification Center on the iPad an abomination (c'mon, you gotta admit - Apple really dropped the ball on making this thing look attractive!), plus this "problem" that you've mentioned, have led me to own one of the two side-loading notification center tweaks: MountainLionCenter for iPad. There is also MountainCenter ($2.00, USD), but it doesn't work as well for me as the free tweak does.
So, to answer your question - no, you can't pull the NC all the way down. But, if you get one of the two tweaks I mentioned, they load from the side and DO take up the whole side. Like this:
Which I find much more attractive. Of course, and as always - YMMV.
Marilyn