I am having approx. 31 8-top tables at my reception and am working on centerpiece ideas. I'm hoping to make them, or at least some of them, myself & want to make sure they are proportional to the table size. How big in diameter should the centerpiece take up on an 8-top table (which I assume is between 60 & 72 inches)? I'm mostly asking in reference to the mirrors that I plan on using underneath the flowers, etc. Thanks!