Yup, that's exactly what I was going to suggest. I'd just choose one of the stacks and record close up. You'll still hear the chompers between songs but during the music the stacks will dominate most of the crowd noise.
As far as recording both stacks for stereo, I've owned multiple recorders/rigs for a long time and it's not unheard of for me to find a place near a stack to stash one of my rigs and just let it record into either one or both channels, then I stealth the stack on the other side. Requires a bit of skill in post to create the master recording, but nothing too technical. It's mainly about matching the length of the two recordings using the stretch tool since two separate recorders will never synch up perfectly over the course of...say...a two-hour show. By the end, one recording will be longer than the other by some numbers of milliseconds. If you join them together without any stretching of one to match the other, the mix-down will start out sounding fine, but by the end of the recording you will start to hear a reverb type of effect. Or if the time difference between the two recording is more than a few milliseconds, the effect is more of a slap-back effect.