There are two foam dividers back there. On the left, one holds the air compressor and jack. There is nothing under it.
On the right, the foam pad keeps the CLP/SSM in place while giving you a storage pocket for tools, etc.

The middle is the floor of the trunk, tap on it, it's metal. Directly below it, is the exhaust system.

There is no spare tire in the CRossfire.

Removing those pads requires you to take the trim out of the entire trunk - not an easy process but not impossible.
It is easier with a kit like this off Amazon, it has the tools that make taking those "rivet things" out much easier!



To remove the trim, plan on 15-20 minutes to 1/2 hour.
To re-install the trim, plan on 1/2 hour up to maybe an hour.

Take out either side first, then the middle, then the other side.
To put things back, I found it best to put the middle in, then do each side, one at a time.
You will want to have a kit of spare "rivets" of all sizes in hand before you start - you will find that some are useless after being pulled out, they deform and won't hold well (the four in the top of the middle section are probably the ones you will replace, I had to, on the two cars I worked on).