Ever hear of the Spruce Goose?
http://www.truveo.com/maiden-flight-of-hughes-h4-hercules-spruce-goose/id/766799794
But Carranza's plane was reportedly made of modern, lightweight materials. Perhaps the bulkheads were made of wood?
"More than confidence would be needed–namely aircraft like Lindbergh's Spirit of St. Louis. The relatively heavy biplanes–all wood construction with water-cooled engines–then being built in Mexico's Talleres Nacionales de Construcciones Aeronáuticas (National Aircraft Factory) had payloads that were too small for long-distance fuel needs. Some American manufacturers, however, were using chromium-molybdenum-steel frame tubing. The alloy's strength permitted lightweight, thin-drawn tube walls and drag-reducing streamlined designs. And radial engines made air-cooling more efficient. The metal-framed, radial engine Wright-Bellanca monoplane had reportedly impressed Lindbergh because it could cruise at least 15 mph faster, burn only half the amount of gasoline and carry double the payload of the old de Havilland D.H.4 in which he had flown the mail.
The planes Carranza and Fierro flew to Mexico City in May 1928 utilized these modern technologies. The Ryan Brougham, a commercial version of Spirit of St. Louis, could lift 2,000 pounds more than the Talleres-built Quetzalcoatl that Carranza had flown to Ciudad Juárez. And BC-2's 2,068-pound payload was 50 percent greater than that of Talleres-built two-place fighter-bombers. But while Carranza's México-Excelsior was built in the United States, Fierro's BC-2 had been made at Tijuana, Mexico."