Glued, dual-wire-modded button CN1 wiring harness
Based on my earlier failed experiment, I learned that piggy-backing a second set of wires from the metal connectors on the inside of a wiring harness can be a clean way to get connections running to both PCB's. So I did the same thing for all of the buttons (X, Y, A, B, Start, Select, Home, etc.).
Another approach here could have been to solder secondary wires from each of the quick-disconnects that are plugged into the Seimitsu buttons. Remember, this mod also has a Remora board, so I didn't see an easy way to join wires together on the Remora board like you can do on a normal MadCatz fight stick. I didn't like this approach because it would have had a bunch of individual wires running from each of the buttons to the ChimpSMD, and it wouldn't have looked as clean.
I could also have stripped a section from each of these wires and soldered to those spots, like Donovan did here: www.donovanmyers.com/2010/02/dual-mod-a-mad-catz-fightsti... But I was concerned that this was going to be potentially fragile and not look as good. I was also trying not to use black electrical tape unless I absolutely had to.
I'm actually very happy with how this turned out. I disconnected these metal ends from the wiring harness plastic piece, tinned the back of these connectors, then soldered 6 new wires to the backs of these. It was relatively quick, pretty easy, and the result is fantastic. Instead of having a bunch of wires coming from the buttons, running to the ChimpSMD, I have 6 wires in a clean bundle, running from the back of this wiring harness.