Le me see if I got this right: with 4 GCX loops modified to stereo I can run the Lex in stereo, go LR from it's stereo switcher out to the VCA on the DMC stereo in. Then stereo in to the Mix 1 In 1 and use two Y cables from the 2 passive splits so that the 2 L channels go to the L inputs on FX 1 & 2 and the 2 R channels go to the R inputs on FX 1 & 2. Is that correct?
Do you think that splitting the signal with the Y cables will cause any issues to the signal: noise, ground loops, s/n ratio...
The source of this signal is one of two preamp outputs. There should be no problem splitting this line level signal.
Now go plug this stuff in and try it out already!