This is a stack tape + stage sound + ambient room sound situation. < Those are the three primary acoustic parts which are going to affect the recording, and I suggest thinking about how to go about capturing those elements in proper balance with each other first of all. Secondary to that, consider ways of getting a playback image which doesn't sound lopsided.
Working backwards let's start with the image-balance secondary aspect thing, which is easy to manage yet counter-intuitive - some mic setups will accommodate a lopsided image-balance better than others, but regardless this general recommendation always stands: Point the entire array at the apparent acoustic center of the sound as heard from the recording position. Don't trust what you're eyes tell you with this! Stand where you will put the mics, close your eyes, try and forget where you are, and turn your head to find the best balance while a band is playing. Then open your eyes and turn the top part of your stand or clamp-rig or whatever to rotate the entire mic setup until it points in the same direction. In this situation you'll probably end up with it pointing more or less straight ahead at the right PA speaker. But it could be slightly to the left of the right PA if the bands onstage sound is loud compared to the level of the PA, or could even be slightly right towards the wall if the wall is very reflective. Don't overthink this part and try to compensate for being off-center by pointing your rig towards center stage or the left PA speaker way over on the far side or whatever. That will only make the off-center image balance situation worse and sound more unbalanced on the resulting recording. Just aim the whole setup in whatever direction sounds most balanced.
More on the first part when I can..
[kuba e posted while I was typing- yes, I used my outdoor 6 channel OMT spaced omni setup indoors two evenings the weekend before last in almost this exact situation (mirror imaged actually, I was on the far-left side) and was astounded how well it worked, as that was not designed with either small rooms nor far-off center recording positions in mind. I've been thinking alot about why it worked so nicely given those constraints since, and I'm going to revise my "small room OMT variant" recommendations somewhat. But yeah, photos of that are in the new Oddball Mic Technique Thread part 2. More on all this later..]