A method of manufacturing a first cured part and a second cured part, the method comprising: positioning fibrous material on a tool surface of a tool, the fibrous material having a configuration of a single structure, the single structure comprising a first part and a second part that are symmetric on opposite sides of a dividing plane through the tool surface; curing the fibrous material producing a single cured structure, the single cured structure comprising a first cured part and a second cured part; and, dividing the single cured structure into the first cured part and the second cured part along said dividing plane through a hollow portion of the single cured structure producing a first cavity in the first cured part and a second cavity in the second cured part on opposite sides of the dividing plane, the first cured part and the second cured part being separate parts after the dividing; producing the first cavity with a configuration for receiving a first fitting in the first cavity for attachment of the first fitting to the first cured part; and, producing the second cavity with a configuration for receiving a second fitting in the second cavity for attachment of the second fitting to the second cured part wherein the fibrous material is in the form of a plurality of sheets of fibrous material, the single structure formed by the plurality of sheets includes a base panel having a bottom surface that engages across the tool surface of the tool, and an opposite top surface, said base panel having a length dimension that extends along the length of the plurality of the sheets configured as the single structure, said base panel having a width dimension that extends between a first end edge of the base panel and an opposite second end edge of the base panel, the plurality of sheets in the configuration of the single structure also comprise a plurality of stiffeners formed in the plurality of sheets, said stiffeners being formed as top hat stiffeners (72, 74, 76, 78, 82) that are spatially arranged across the base panel top surface from the base panel first end edge to the base panel second end edge, said top hat stiffeners (72, 74, 76, 78, 82) having length dimensions that correspond to the length dimension of the plurality of sheets; wherein the top hat stiffeners (72, 74, 76, 78, 82) have cross-section dimensions and hollow interiors that increase in size as the stiffeners extend from the base panel first end edge and the base panel second end edge toward the top hat stiffener at the center of the plurality of sheets with the center top hat stiffener having the largest hollow interior. positioning fibrous material on a tool surface of a tool, the fibrous material having a configuration of a single structure, the single structure comprising a first part and a second part that are symmetric on opposite sides of a dividing plane through the tool surface; curing the fibrous material producing a single cured structure, the single cured structure comprising a first cured part and a second cured part; and, dividing the single cured structure into the first cured part and the second cured part along said dividing plane through a hollow portion of the single cured structure producing a first cavity in the first cured part and a second cavity in the second cured part on opposite sides of the dividing plane, the first cured part and the second cured part being separate parts after the dividing; producing the first cavity with a configuration for receiving a first fitting in the first cavity for attachment of the first fitting to the first cured part; and, producing the second cavity with a configuration for receiving a second fitting in the second cavity for attachment of the second fitting to the second cured part wherein the fibrous material is in the form of a plurality of sheets of fibrous material, the single structure formed by the plurality of sheets includes a base panel having a bottom surface that engages across the tool surface of the tool, and an opposite top surface, said base panel having a length dimension that extends along the length of the plurality of the sheets configured as the single structure, said base panel having a width dimension that extends between a first end edge of the base panel and an opposite second end edge of the base panel, the plurality of sheets in the configuration of the single structure also comprise a plurality of stiffeners formed in the plurality of sheets, said stiffeners being formed as top hat stiffeners (72, 74, 76, 78, 82) that are spatially arranged across the base panel top surface from the base panel first end edge to the base panel second end edge, said top hat stiffeners (72, 74, 76, 78, 82) having length dimensions that correspond to the length dimension of the plurality of sheets; wherein the top hat stiffeners (72, 74, 76, 78, 82) have cross-section dimensions and hollow interiors that increase in size as the stiffeners extend from the base panel first end edge and the base panel second end edge toward the top hat stiffener at the center of the plurality of sheets with the center top hat stiffener having the largest hollow interior.