I have had this situation. I created an "Amp and Cab free" preset that just had my required effects on it. Basically a stomp box style setup and ran 1 cable straight into the front of the back-line amp - which was a Vox AC30. Ironically, this was the very first time an FOH engineer came up to me and went "Fractal AX8" Nice ... you should ave gone straight into FOH as these things sound amazing" Doh! With all of that being said, everything sounded great. Maybe you could just AX8 Stomp Box style for the night.