Mine was very easy to install....clean the glass, center the piece, stick it down and pull the covers off the double-sided tape. Done. Looks great and fills that funky gap with something besides leaves.
The only thing you need to watch out for...don't mount it too close to the trunk lid. When you open the trunk the lid moves forward slightly, if the piece is mounted too close it WILL rub. Worse in the winter when everything's cold. They include some small rubber pieces for setting the spacing. You need at least an eighth inch spacing, maybe a quarter inch to be sure....but closer looks better. Stick it down loosely and see if the trunk lid clears it...if so then you win.