Using Arduino 2560 Rev-3 as HID keyboard

The board has Atmega16U2, which is to be flashed with Arduino_Keyboard-0.3.hex in order to make a hid keyboard (http://mitchtech.net/arduino-usb-hid-keyboard/).

The provided link has unusable HEX files for the chip but i am using the keyboard.hex from http://hunt.net.nz/users/darran/weblog/b3029/Arduino_UNO_Keyboard_HID_version_03.html & UsbSerial.hex from the Arduino IDE folder.

Mostly the tutorial-links are for Arduino-UNO (http://forum.arduino.cc/index.php/topic,111.0.html).

After setting the board in DFU mode and flashing it with the HEX, the board wont get recognized. Can someone suggest me a way to make HID Keyboard (3-keys) on Arduino 2560 Rev3? or is it only possible on UNO & Leonardo ?