I have only four mics so I would be obliged to look at a pair of omnis or cards in the sweet spot with the angles and distances as outlined by Williams in Stereo Zoom. Or, a pair of cards in the sweet spot, or as close as I can get, angle and spacing as described by Williams, and a pair of flanking omnis. John Eargle likes this setup. Multi-mic'ing can introduce as many problems as it solves, though. Less is more.