Embodiments provide methods and systems for treating aneurysms using filling structures filled with a curable medium. An embodiment of a method comprises positioning at least one double-walled filling structure across the aneurysm and filling the structure(s) 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 while 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. The medium is hardened while the lumen remains supported by the balloon. The balloon is then removed after the medium hardens.