Systems and methods are provided for creating precursors for consolidating composite parts. One embodiment is a method for forming a metallic structure. The method includes forming a precursor for a pressure membrane that includes a contour having a linearized length corresponding with a linearized length of a surface of a forming tool. The method also includes affixing a perimeter of the precursor to a perimeter of a base member, leaving a volume between the base member and the precursor, altering a shape of the precursor at a superplastic temperature by forcing the precursor into complementary contact with the surface of the forming tool, and setting the shape of the precursor while the precursor is held in complementary contact.