Interesting work Mr. Monkey
I've a complete grill block and an air dam that is just 3-4" above the road. My rad fan comes on all the time, however I spend enough time at speed on the highway, I've just let it go figuring it would be a net gain (no idea if it is, I need to test this but I only see a minor increase in gph readings when the fan kicks on) My cooling fan kicks on at 215 then off again at 200. I just let it cycle between these temps. In really hot summer traffic, I've seen 225 when the high speed fan kicks in. Doesn't worry me much because the fan keeps things under control.