I spoke to Fender…( what a concept)…slaving these combos IS an option using the FX loop, and both amps will produce output…at least in THIS case, the Send output will not cut off the speaker’s output…
But I’ve decided to try the best of both worlds. I now have a used, sub $200 Ampeg B2R driving a used, sub $130 GK 410, and instead of simply adding a 115 cab to this, I’m using the FX Send to a used, sub $150 Acoustic B200 MKII 115 Combo…low end for days, plenty of headroom to keep up with any drummer…TWO drummers!..and a relatively articulate sound eminating from my 410…who knows, at some point, I may even add another used 115 cab to drive the Ampeg down to 4ohms and use it’s 350watts…
anyway, thanks to all who posted here, shared their support, know-how, comments, dismissals, questions, etc…now looking forward!