Hello RobG!! You have done what I was planning to do for this Christmas with WS2812!!
I have a little experience with Pics using CCS compiler but never put my hands on Texas microcontrolers.
I think that now is the time, because what you have done, will help me with the idea.
So, I think that what I need is control the lights with a computer conected to your Ethernet (e1.31) 4 universes DMX board. And then, four RS485/WS2812B boards (one on each port).
How many pixels do you think that this will be capable to move? (512*4)/3 = 682 pixels?
How many frames/second with max load?
What free program do you recomend to control lights from PC?