I have a FF275 kit with their header, cat, and exhaust. It is tuned quite richly to keep temps down and yet I still started to melt the trunk floor when I was running a track day with back-to-back sessions. I forgot to take the trunk carpet and foam out and I do not have a rear panel eliminator (yet). Nothing came lose on my car but it still started to melt just from the exhaust and header heat.
I have now decided to get a rear panel eliminator (even though I don't care much for the look) and I will get some additional heat shielding installed.
Be careful out there, guys!