Questions to think about: Do you know if the mix is going to be mono or stereo? Where will the stacks be?
If the mix is not stereo, then it's possible to obtain a decent recording from a side-rear location. Emphasis on Decent.
The likely best option for you is to run your card's in parallel to each other..., and point 'em at the stack you're probably going to be facing. If that's the case, you'll get a decent sense of mono, and the loss of stereo will make it sound more like you're just where you are.
If you had omni's, or a really weak cardioid pattern, you could also just point them at either side. Reflections might make it muddy, but you'd get the stereo-ness of the room.
Another thought, thinking back to a Flecktones show I did where I was house right and basically in front of a set of stacks... [Reading, PA show that should be on archive.org if I remember correctly]: point your left mic at the stack. Point your right mic at about 45 deg away from that. It'll make your soundfield a little strange, but you could get some stereo-effect from that, depending on your pattern. It's not ideal, but try it out for the opener.
Best bet is still to point at stack, in parallel. It'll sound mono, but better than nothing.
Is no one else taping this show? If they are, you can always try to clip onto their stand if you have the right stuff.