How should I mike our congregation with PZMs?

I am responsible for the sound reinforcement system in our church building. My current project is congregation/house mics. Our auditorium is approximately 50' x 50' with an aisle down the center, The ceiling height is approximately 13 feet. We have a center cluster of speakers in the front (two speakers, one pointed toward each side). We have about 250 seats. What PZM should I use for recording (PZM30D/6D or PZM185), and how many (one only in the center, or one per side). Stereo is not important. 

We have an acoustical tile drop ceiling. What is the appropriate mounting technique for whichever mic you suggest? 
Randy E. Bowman, President 
Bowman Construction & Design, Inc. 

Reply: We recommend using one PZM-6D on the ceiling in the center of the congregation. You can mount it with four bolts and nuts, using two washers per bolt. For each bolt, put a washer above the ceiling panel, between the panel and nut. On the bottom of the panel, trap the PZM plate between the panel and the washer that is next to the bolt head. The washers above the panel prevent tearing of the acoustic tile, and the washers touching the PZM plate hold it in place against the ceiling.

The PZM-6D is recommended because it is small and light weight, is 19 dB more sensitive than the PZM-185, and has a flatter high-frequency response.

As an option, you might want to delay the group mix of the stage mics before mixing them with the audience-mic signal. Set the delay to 20 milliseconds at first, then adjust it up or down until the signals of the stage mics and audience mic coincide in time. You could play a click or metronome through the sound system, and adjust the delay while listening to the stage/audience mix over headphones.