Thanks for the advice!
I currently have 3 other panels underneath the car, placed around the exhaust and smoothing out the underside (I have a thread on that in the Ecomodding Central forum:
http://ecomodder.com/forum/showthrea...ign-12096.html )
I'll see about lowering the front of my undertray and get it closer to horizontal. I'll need to pick up some longer screws, though.