I made a spacer for the iPhone5 Car Cradle (http://www.thingiverse.com/thing:30510). This space will fit a RAM Base w/ ball (http://www.rammount.com/CatalogResults/PartDetails/tabid/63/partid/082065077045065045050051056085/Default.aspx).

This spacer would work for anything you want to add a RAM mount to as long as it's big enough to glue.