After reading the forums, it seems that the factory cargo cover wasn't ideal. First off was the price (~$300), then there is the issue if hitting your head. I really like the soft retractable cover from my Prius but that's not available. So I decided to build my own. The total bill is ~$27 and it took about an hour to make. I like the fact that I can fold it up if I have big cargo and it doesn't look too bad from the outside either. It's just black.
This cover is 37" x 42.5", connected at six points around the trunk. This lets me remove it quickly and fold back as much as needed. The parts list is:
2 yards of black heavy-weight fabric = $6.00
Grommet/Eyelett kit = $14.00
2 sets of command hooks = $7.00
Final fabric with grommets. The top has room for a future dowel to provide stiffness. Make sure you hem the have enough spare fabric to hem the edges. I folded the fabric over to form three layers so the grommets could grab properly. I bought two yards and it's about 45" in the short dimension (uncut).
Grommets. I chose the silver ones so that they were easy to find on black fabric. :