Thank you, and yes, I'm enjoying it very much. The project cost more than I thought it would, and I had spent around $5500 when I got it on the road. Since then, I've only spent about $65 on materials for mods.
I threw together an engine bay undertray out of coroplast Thanksgiving morning, before heading out to my mom's house. I didn't make an attempt to measure the aero impact of the tray, but the temperature impact was very small. Probably +5°F to intake temperature.
The tray is held on by four bolts, and I didn't even have to drill holes in the car. I cut away plenty of coroplast for the tires and control arms to move through their full range of motion. Once I get the final front bumper cover in place, I'll see if I can do a better job of keeping air away from the wheels and out of the wheelwell.
Lately, it's been 35°F and rainy. It takes the car 6 mi @ 60mph before it's mostly warmed up, by which point I'm more than halfway to work. I thought the tray would help, but it doesn't. So I had a crazy idea: block 100% of the radiator with a sheet of coroplast:
Initially, I thought to set the coroplast in there, then cut a generous hole for the radiator. But then I thought, why not test it with 100% blockage? The results were surprising: it still takes forever to warm up!
At 60mph in the rain, with the radiator fully blocked, the coolant temperature quickly rose to 120°F, then slowly rose until it settled at 165-180°F like it does on particularly cold and wet days. I turned the heater control to "cold", and it eventually got up to 195°F where it belongs.
Is it supposed to take that long to warm up?