I have now made some mock-up aero attachments to test for drag variations on the Insight.
Strakes to go in the rear diffuser:
Side skirts:
Rear spoiler that can be positioned at two heights:
External front air curtains (and also can be trialled as propulsive wing elements for front bumper corners):
All (except for the wings) are in plywood that can be taped into place and easily removed. (Wings are GOE222 aluminum profile.)
I actually wonder if any of these will make any measurable changes in drag (plus or minus), but we will see.
Am also going to try the Insight with the rear wheel spats (side covers) on and off.
Just waiting for the rain to stop. (Here in southern New South Wales, Australia, we've been in drought for years, so can't complain when we start getting some good days of rain.)