I don't know if this is along the lines that you all are looking for, but one common method of creating a faux ceiling beam is to nail 2x4's along the ceiling where you're wanting the beams. Next create a "U" shaped beam with the inside width 3.5 inches (to snugly fit the 2x4s). Then attach the faux beams to the 2x4s, screwing/nailing from the sides. This will create the illusion of a solid beam, especially if you take the time and effort to mitre the joints. Hope this helps (I know it's not the styrofoam beam that you all were talking about).