A quick drive around town reveals that the top gap cover is staying down and in place while at speed. Not sure how much air will cause it to flip up but I'm not gonna worry about it too much as the cover can't flip up and over on the hatch so it should fall back down on its own.
Where the longer 48" cover was flipping up on the outside edges, I haven't noticed the 24" long flipping or fluttering at all.
