[thstone]

I went out and looked at my car to compare and if it were me, I'd re-install the cat heat shield. Those cat's get mighty warm and if your rear trunk is anything like mine, you could roast a pig in there most days so I'd want to keep as much of the heat shielding and protection in place as possible.

Also, I'd worry that the underbody heat shield may not have been designed for the direct heat from the cat (thus the reason for the all-metal heat shield) and might break down over time.

But then again, you might be fine without the heat shield, hard to know for sure.