I've been using the same pipe insulation grille block all winter on my 2010. Mine kept popping loose at the ends {they are nearly full width, even though the grille openings are not}, so I used zip ties to hold them in place. When the weather has been really warm, I've opened the zip ties back up so I could remove a strip and run with three. I was too lazy to do any a-b-a testing, but I've had some of my best mileage figures this way.
Of course, when I took it in for the recall reflash of some inverter, I removed all three strips.
Care to share more details on the rear wiper delete mod. It looks so clean, almost as if it were never there.