Methods and systems for treating aneurysms using filling structures filled with a curable medium are described herein. Such methods can include positioning a double-walled filling structure across the aneurysm and filling with a filling medium so that an outer wall conforms to the inside of the aneurysm and an inner wall forms a generally tubular lumen to provide for blood flow. The lumen is supported with a balloon or other expandable device during and/or after filling. The pressure within the structure and/or in the space between an external wall of the structure and the aneurysm wall is monitored and a flow of the medium into the structure is controlled responsive to the pressure. The pressure can also be used to determine a filling endpoint.