Hmm yeah I've seen the photos of your CRX.. My thought was the large flat space on the rear is a great place for air eddy currents to get you.. extending out the rear by a foot or more should not be a issue.. however I'd like to get the rear section to a smaller size to reduce eddy currents.. Like the airplane drawing above it seems to be a more flowing design...
I assume anything will be a improvement.
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