Hi,
I do like having a digital camera! (Nikon D40X) Here are some pictures of the current collection of aero mods on my xA:
I've significantly closed down the front air intakes, and yes the coolant temps are completely fine -- come winter, I will have to close them even more; if not completely.
I've added the foil tape to the front rims -- this probably only helps marginally. I need to make some Coroplast fender extensions to the front and top of the front wheel openings.
I've removed the front mudflaps. This should have been done ages ago! I think it has helped me gain ~0.5-0.8mpg, at least. The average climbed that much in ~100 miles, on a 300 mile average.
The rear wheel skirts are now shorter (like the acrylic ones I made first -- I found that when they stick out into the air stream, they don't help as much. The lesson seems to be cover as much as possible without protruding into the air flow -- it is better to cover less, and stay as flush as possible. These still stick out a little bit (using the 1/8" steel rod inside the bottom corrugation tube), so they clear the tire and the wheel -- but this is a very gentle sloping wedge.
The rear underpan has a bit more tape on it to be sure to hold it firmly in place, and to minimize air getting in above it...