Reply to Behringer ddm4000 crossfader mod

http://youtu.be/dbuPNuSOuos

I found a cheap DDM4000 on cl with the intentions of doing this mod. I was wondering what is actually happening in this mod? Im guessing that the midi from the up fader is being routed to the crossfader to do both midi/audio at the same time. My question to anyone that can answer is does it have to come from the up fader. What i would like to do is take out one of the potentiometer from either the sampler or mic input that are midi controllable and route those to the crossfader instead.

If possible i would just need to know pinout and route the midi signal to the crossfader.

Any insight for this issue is GREATLY appreciated!!!