[freebeard]

I'm looking at the rear of the vehicle, I imagine the A-Pillar vorticies have already done their damage and are decomposing, it's more the C-Pillar vorticies that I was referring to which rotate in the opposite direction to the A-Pillar ones.

I went back and looked, you're right.

So the question really is if the rate of change is reduced in centre of roof line and lower sides, can this compensate for the more rapid change coming down and in from the corners and hence reduce risk of C-Pillar vorticies.

I'm not picturing it. Are you talking about the tow vehicle or the trailer?

How about a half-rounded trailer with blisters right behind the orange area. Something larger than a running light but smaller than an aircraft canopy. To offer something for the air to reattach to.