hey dave,
Sounds like high ceilings, which is a nightmare. If I were taping it, I would probaly ask the guy running mix if he is running stereo. For a small event like that, it is likely he is running mono. In that case I would bring the AT as close to one of the speaker cabinet sets as possible, trying to point it in between the sub cabinet and the high. Tilted slightly away from the subs. I'd walk up to them while he is playing pre show music an move my head around till I found a sweet spot and put my mic right there. Those AT's can take the pressure levels, if you can.
If it's stereo, and you are running XY, position youeself as close to the speakers as you can while still being able to see the front of the high freq cabinet pretty well. Again, listen. thats the best way to tell. Opening bands are great for that. That's what I would do, however... I am sure there are alot of well calculated ways to approach it. Listen, then setup.
Good Luck!
Bri