Thanks Xzin, one further question, were you able to simultaneously press different keys on different X-keys and have them register properly?
Yes I was. It acted just as if it was one HUGE keyboard (with, I think about 220ish keys if you count the PS/2 keyboard, the two Pro's, the stick, the 2 desktops).

If I were to continue my setup, I would program the PS/2 X-keys with foreign characters and use left/right shift/control/alt to control everything. When I was playing, there was no distinction between left and right modifier keys. That helps quite a bit but still, I don't want to accidentally hit keys typing with say, shift held down. I posted about this before, I am sure you could find it on a search. I know I talk about it briefly in my 10 boxing guide.

My difficulty with programming them is the PS/2 needs a pass through device to record off of. I tried using a barcode scanner but barcodes are, by their nature, limited to normal keysets to avoid confusion or errors. My next step was to buy a cheap foreign keyboard or even use a computer to output PS/2 scan codes but I never got there before I stopped playing.