Hi Matt this looks great, I think if you have time you can still play around a bit on the animation side and how your ufo moves. (Don't get me wrong, it doesn't look bad at all so far)
I might suggest this technique too often, but it is a simple way of getting your cg footage to "sit" nicer on life action shots. It basically makes some of your backround footage to spill a tiny bit of light onto your cg stuff. And it's all done in post.

here's the link

https://forums.creativecow.net/cgi-bi...ill/index.html

looking forward to see how it goes.