perhaps sell one of them to Andy:http://www.network54.com/Forum/580706/thread/1201816817/last-1201816817/WTB+1952+Mantle+%23311>and use the cash + card for trade as you'd probably have an easier time finding someone looking to trade down but not wanting to have 2 of the same card.
1952 Topps Mantle - Trade Up?