The Liquidware TouchSlide display uses the 2560 so you should be able to use the core files from that to get it to work. It works great and is fully arduino compatible. You can get their libraries from github/liquidware
Here is the entry from boards.txt
##############################################################
#Board Description
slide.name=TouchShield Slide
slide.group=Arduino
slide.build.core=touchshield
slide.build.mcu=atmega2560
slide.build.f_cpu=16000000L
slide.reference=hardware/cores/arduino/reference/index.html
slide.upload.protocol=butterfly
slide.upload.maximum_size=250000
slide.upload.speed=57600
slide.upload.mcu=m2560
#ANT core targets
slide.targets.sketch.verify=build.all
slide.targets.sketch.upload=upload.sketch
slide.targets.bootloader.upload=upload.bootloader