Happy New Year year!
I have tried the 4CM, however, I have got too many gears so finally, I switch from 4CM to 3CM (or 7CM) as follows:
guitar -> GR20 stereo out-> Roland KC 500
GR20 guitar output -> GT8 send -> Mesa boogie amp input
GT-8 L output -> Mesa boogie FX return 1
Mesa boogie FX send 2 -> DigiTech TSR 24s -> Mesa boogie FX return 2
In this case, If I bypass the loop of my Boogie, I can use Boogie's preamp without mixing with the GT-8 preamp; as I have set the loop on my GT-8 after the preamp, so I still can use my GT-8's FXs. Seeing that my Boogie preamp got some noise, I have from time to time turn on the noise gate of my TSR 24s by switching the FX 2 button on my boogie foot controller on. If I turn the loop (FX 1) on, I can then switch on the GT-8 and bypass the preamp section of the Boogie, so now I have my GT-8 back with 4 different power amp sounding (my Road King have 4 channels) selectable.
The trouble is, if I use only one cable plugged in the Boogie, it rocks without unwanted noise, but if I once turn on the GT-8 power (with the 3CM), noise kicks in. I still can't find the "twisted pair" cables u mentioned. I wonder will this noise problem be solved by replacing my cables, or which cable should I replace actually?