I don't have the sysex from the manual in front of me but there is a field which contains the MIDI channel in the least significant nibble of a byte. I think its called the "format" byte. Just set the lower 4 bits to the current MIDI channel setting of your DW-8000 minus 1. So, if your DW is set for channel 1 make it a 0, for DW channel 8 make it a 7, for MIDI channel 16 make it an F. If you have more questions feel free to email me at SpazTech@aol.com. Or save yourself a little time and check out my (inexpensive) librarian at:
http://members.aol.com/spaztech/SpazDW80.html