Ok this is a completly ridiculous idea. But I was thinking of it during class today. Perhaps you could add some side vents. Normally in the engine area, but maybe you could blend one in the trunk area if you dont mind cutting a hole or two. While you wont get colder air, you'll get some faster moving air in there and move the super-heated air out.
Again I was thinking of this during class, just a thought
Jeep Grand Cherokee Laredo
Kenwood X790 x/ iP500 Ipod Interface
Elemental Designs 13Kv.2 D2
CDT ES-620 (omg yayay!!!1)