550 vs 660 – (Rear) Bumper(s) of fun

The 660 rear bumper is wider than the 550 by approx 10mm

But where exactly is the extra width on the body? Using the earlier CP21S Vertical handle VIN to compare it’s still unclear where the width comes in.

CM11VCP21S VertCP21S Hori
Door68001-60D30-000 / 60DV0-X0668001-60D30-000 / 60DV0-X0668001-60D60-000 / 60F13-000
Side Panel64111-71B00-00064111-71B00-00064111-61D00-000
Rear Bumper71811-71B00-26U / 71B00-79971811-61D00-79971811-61D00-799
Rear Bumper Panel65410-70B00-00065410-70B00-00065410-70B00-000