I have a ren64 with dmx software. The problem is that you are looking at the ren64 as 8 separate controllers. I made a small hardware mod cut the tx out of the last pic and added a link so that the dmx input was connected to the DMX output.
now I have a 64 channel controller that operates like any other dmx controller. I then added the Start address code from the modified JEC pixel and now I can set the start address of the First controller we do not care about the method that is used to send the data through the rest of the pics.
It would not take much to change the code in the PIC to look for the start code 91 and when it sees it go into program mode read the program packet and update the First pic's Eeprom. These program packet bytes would not be feed through to the next pic . This would allow all pics to have the same code.
Just my two cents worth.
regards Jeff Rae
Start Address open source code
http://code.google.com/p/open-source-lighting-control/source/browse/trunk/DMX_DCSSR/Software/DMX_DCSSR.asm?spec=svn13&r=13