NATURAL BRIDGE - This kind of madness requires planning. It took weeks for artist and oddball Mark Cline to reach this point. Monday, he stood on a hill by U.S. 11 with the dust devils, his sidekick Victor Reyes Peres and a disassembled life-size Styrofoam replica of Stonehenge. They awaited a kind, portly old guy named Hershel and his concrete truck. There may be other imaginations unregulated enough to conceive of "Foamhenge." Not many could pull it off. Not many would even try. But they are not Cline. In fact, the madness of Foamhenge may not be in the mere...