For those running XY, one thing to try is adjusting the included angle. If it's a crappy sounding room, 70º - 90º may work best since it will minimize the effects of the room and crowd while still maintaining a stereo image and soundstage. (Below ~70º, the soundstage often collapses to mono-ish.) If it's a really good sounding room, 90º - 110º may work best because it will help open up the stereo image and soundstage. Basically, don't get stuck thinking you've gotta run 'em at 90º with XY.
That said, I ran Blumlein last night on-stage for Eastern Blok (pka Goran Ivanovic Group)...mmmmm...Blumlein...