Front portion of the undertray is in place & fastened. I got most of the center section done this evening too.
I - gasp - drilled holes in the underbody to fasten the coroplast. I think that's the real reason I've been procrastinating. I just feels so wrong to drill underneath - thinking of rust.
Once all the panels are in place, I'm going to do a B-A test, where I do some runs with the full tray, then remove it on the roadside and repeat the runs. I'm not doing A-B-A. Too complicated.
After the test, I'm going to have the car professionally undercoated and then put the panels back on.
The trickiest area left to do is the rear control arms. They hang down LOW into the flow - they're located about at the halfway point between the road and the bottom of the rear bumper. I'm thinking I may try to use the coroplast to extend them backwards in a teardrop shape. Complicated, but they're definitely a drag problem the way they are now, all blunt and exposed to the flow.
Anyone want to make any guesses on what the tray is worth @ 55 mph? After seeing the effect of the unloaded roof racks on the top of the car, I'm cautiously optimistic that the tray could be significant - I'm smoothing out some serious "excrescences".
You mean the whole undertray itself vs. not having one?