Jules,
congratulations on the ENGL, it will rock your world.
I normally keep the amp in the control room, in a place from where I can hear the control room monitors fairly well, so I can make changes to the sound of the amp listening through the microphones. Also, IMHO it's better to have a short guitar cable than a long guitar cable and a short speaker cable (especially with a powerful amp like the 120). I hate talkback switches and the communication with the musicaian is very important. If you do need feedback, have the guitar player touch the cabinet of your control room monitors with the headstock of the guitar, but don't let him anywhere near the actual speaker for obvious reasons. In cases of severe feedback, you might want ot put him in the live room for that part of the recording.
Have fun, can't wait to hear the results
