The stereo mod is carried out by voodoo lab, John Clark can help you... Or send an email to email@example.com
Hooking it up is a breeze, as you only use 1 loop for each stereo effect. basically you would wire it like this (and this is very basic and I apologise if any of this isn't clear)
Loop 5 Send > Insert Cable > Stereo effect L & R > insert cable > Loop 5 Return > Loop5 Out > Stereo Patch Cable > Loop 6 In
You follow the above system, wiring up your effects for each loop , when you get to the last loop, for example loop 8 you plug in a stereo insert cable into the OUT of the loop, this breaks out into 2 mono jacks..... each jack has half the stereo signal, so you then feed one signal to one amp, and the other signal to the other amp... Et Viola...
And remember that the stereo moded GCX can also be used for normal mono effects.... It's not exclusively stereo, but you have that flexibility.
If any of this is incorrect people, please correct me