So, I was probably right that the side curvature is too aggressive, but some of the flow problems on the lower side originate BEFORE the tail...
With apologies to the colour blind...
- GREEN TUFTS = smooth flow or mildly turbulent
- YELLOW TUFTS = moderate turbulence, but no recirculation (tufts pointing "backward")/separation
- ORANGE TUFTS = high turbulence and some recirculation (tufts pointing "backward")/separation
- RED TUFTS = permanent recirculation/separation
I'm debating doing some reconstructive surgery to reduce the curvature of the lower side panel (ie. increase the width of the "transom" / rear tail light panel).
But the
problem with the flow on the lower side portion is it's not getting clean air off the side of the bumper behind the rear wheel. The air there is already highly turbulent with some recirculation/separation. So relaxing the tail curvature downstream of that isn't really going to help much on its own.