I'm dreaming about an Insight I, but will never have one in France...
I had to talk to a cop about my car and one of the annoying thing he noted about my car is the rear vision :
He told me that I shouldn't block the rear vision as my car was certified with a rear vision.
What is annoying me about that back is that it's in two parts, the airflow jumps from the front to the rear and have to reattach...
I got the idea to use a transparent plastic film :
Sadly the transparent plastic film I'm using isn't transparent at all through the rear mirror... so I unfolded the passenger mirror and moved the camera over the rear plate.
I drove my last tank with this mod. On some points I had the feeling the aero was improved (final speed on down hills), but not on others (lengths of glides). Despite a very bad week (10 mi daily commute driven in 45 minutes instead of a 25 mi one driven in 35 minutes) and every morning with (near)freezing temps and lights in the morning I achieved a winter kilotank so it mustn't degrade the aero...
Have fun,
Denis.