The base of the PZM should always be oriented perpendicular to the sound source. Think of it this way: if you place the mic right side up, flat on the floor, then ideally your instrument (let's use a trumpet) should stand right over, or just in front of the mic, pointing down toward the floor for maximum pick up. If you mount the mic on a portable panel, like plexiglass or sheet rock, connect strings (mono filiment nylon for invisibility) to the four corners of the panel, hang it upside down, over and just in front of the performers, and angled so the broad flat face of the panel, with the mic in the middle, is facing toward the instrument. The PZM is now upside down on the bottom of the panel, and the trumpet player can point forward or up in the air to be picked up over head. Remember, the panel or boundry is just an extension in all directions of the flat base plate of the mic. And to get the best low-end response, the panel should be at least 4 square feet (2' x 2'or bigger) and as flat and rigid as possible. I have not done this, but I have heard of people making the mic somewhat more directional by placing a large block of sound-absorbant material over the back half of the mic, just behind the opening slot, with a cut-out to fit tightly over the mic body. That way, theoretically, the mic picks up in a 1/4 spherical pattern from the front.
Brian.