[Christ]

Guys... why don't we taper those skirts up and under the rear bumper for increased flow into the wake with minimal arc in the direction change?

If you start right at the back edge of the wheel opening, and fold the skirt under the truck/car while tapering it in, you end up with a nice path for flow to... well, flow. as opposed to a square edge for flow to separate from. You also get the benefit of tapered bodywork adding more of the flow into the wake, creating less of a low-pressure zone.

Effectually, this would turn the rear body work into a boat-tail of sorts, especially when included with a rear belly pan.