@ rayvillian, I agree with the air build up behind a tow vehicle and in front of the trailer. bad karma. And the square back there are always possibilities. I forget the elf cottage is back there all the time. In fact I think it improves my wind resistance, even if it does add another axle.
There comes a point though when you have to account for your slopes. Mine splits the wind both ways. I need 150% that scale for two inside though.