To be fair, it was buried in an infographic.
I spent some time trying to find an academic PDF that compared solutions for the tractor-trailer gap; maybe someone else can point to it. I did find this
post I made in a relevant thread:
http://ecomodder.com/forum/showthread.php/canard-bluff-bodied-box-33231.html. The post discusses perforated flaps and visors.