A few years back I recorded an unplugged folk trio - two guitars + fiddle, vocals from all three - and set up ~5' back, XY, ~4' up. Played around a little bit with distance and height to get it reasonably right. Too close and you won't have blending / balance from the instruments and vocals and you'll hear the players moving back and forth, forward and back as they sway with the music. Too far and you'll pick up too much room and lose some punch. Somewhere in between and you'll have nice blending of the instruments and vocals with minimal room chatter. FWIW.