We normally put them up. Securing them depends on the size. The small ones (12-15") we do with an adhesive like EE or shortcircuit use. For the big ones (20-36") we glue and put in a few drywall nails near the outside edge. Since they're often styrofoam we use a counter sink to make the indent first then SLOWLY run the screw in to a level of (just barely) below the surface. We get the painter or drywall guy to fill the holes before they paint. Seems to work and nobody has complained about filling the holes for us.
