I have seen the storage area in person. I am not familiar with any "wedge" or "slot" you speak of. I did lift up the floor of the trunk and there was the panels in their sleeve as you mentioned. It was not a Trailhawk that they let you play with at the show and I know those get a space saver tire.... Maybe the panels sit on top of the tire? But with the bigger full size Trailhawk tire I don't how they would fit.
The video linked in this thread shows you the tray. Starts at about 17:10, around 17:38 you can see that the soft carpet layer that covers the spare tire area isn't quite flush with a full length molded in ledge. You cna also see a wedge shaped ledge that sticks out farther and doesn't run the whole length that the hard false floor lays on which creates the gap for the panels. Then a big foam tray under the carpet layer.
From the descriptions I have read, with no spare, you get another tray under that big foam tray that fills the temp spare space. With the full size, you get two kind of crescent shaped storage trays instead of that one big one.
PIcture of the full size spare, you can see the crescent trays don't rise above that molded in full length ledge on the left.
http://www.fourwheeler.com/news/1403-2015-jeep-renegade-revealed-at-geneva-motor-show/photo-14.html
Doesn't mean I'm right, but that's my interpretation of pics and descriptions. Also, upselling you on the TH with options, and then making having those options suck isn't a good plan.