I was curious what this little extra surface on the back of the F-22 is for. I can't see any use of it protruding past the engine nozzles, so what is it for? Also, does the structure have any problems with heating, being right beside the engines? (Especially with the afterburner on)
According to this cutaway (source) it is a "runaway emergency arrest hook housing":
While the cutaway drawing shows that Stinger described as an enclosure for the runway arrestor hook, close-up inspection of an F-22 aft section reveals that is only partly true.
The runway arrester hook is located in a low RCS blister pod just under that structure.
If you take a look at the aft end of an F119 engine removed from the airplane, you see quite a bit of structure surrounding the jet pipe. This contains the actuation equipment for the thrust vectoring paddles.
I would argue that the little ‘stinger’ is more likely an aerodynamic closeout or similar structure between the two engines once they are installed in the airplane.