The channels would not wrap at all, so anything above 4 can be used for something else, with the exception of channel 10 which has a special meaning for the drum channel.
Here is a link to the firmware .hex file. If the file content displays in your browser, just “Save as…” to save it to a file. This is the .hex file you will use in the instructions.
http://synthino.com/downloads/firmware/synthino_xm_midi_nowrap.hex
