I measured the nose of my car (finally) and what I found was; the nose of the car is 9.5 inches off the ground. However, the belly pan under the engine is only 5 inches off the ground. To complicate things, there are also air deflectors that narrow the opening between the front wheels. So, to the best of my calculation, the air is forced into about 40% of its innitial area. So, I will try the chin spoiler at various heights to see what affect it has on the aero efficiency of the car. Obviously, a 5 inch high chin spoiler may be a bit too low for normal driving, but, then again, maybe not. It all depends on the areas I drive in. Maybe I will make a very cheap (I.E. Choroplast) chin spoiler that I don't care if I wreck to test before I make a pretty one.
I also found quite a few ways to clean up the air flow around the nose of the car and under the rear end of the car as well. In fact, a few of these mods will probably look really cool too!
Matt