Reprogramming the 16u2

I intend to build a device to allow my 2-channel RC remote to act as a joystick on my PC. I have a couple of questions:
1.) I know this involves modifying the 16u2 firmware however I would like to restore back if need be. I have the hex file of the original USB/Serial firmware but I can not get avrdude (I prefer to use this instead of FLIP) to recognize the 16u2 chip. Is there a patch I am missing? The 32u4 chip is listed but none of the others in that family.
2.) Would it be possible to modify the Leonardo firmware to install on the 16u2? This seems like the easiest approach to my project.
Thanks for any suggestions you can provide!

I know that avrdude 5.11 and greater support the 16u2 and 8u2.

What version of avrdude are you using?

5.10. I'll update it.

Well, 5.11 did not work but I was able to get it to program in AVR studio. Now to figure out how to make it a USB joystick. Any tips?