I don't know the details, but I understand it's possible to select how much program memory is available for the bootloader versus the sketch. I think this is defined by the fuse settings. Is it possible that the board has a bootloader and fuse settings installed that make less space available for the sketch than you have indicated in your boards.txt? I notice that the error occurred on a nice round hex number which is the sort of thing you'd expect if you were just overflowing the space available for storing that sketch.