By mid-August 1987, the configuration choices had been narrowed to five, represented by Configurations 595-7 (baseline with trapezoidal wings, four tails, and eight missiles); 612 (baseline equivalent with six missiles); 613 (trapezoidal wings and twin tails); 614 (diamond wings with four tails); and 615 (diamond wings, twin tails, and twin side inlets). By late August, the diamond-wing four-tail Configuration 614 won out.

"The fundamental reason for going to a diamond wing was that it provided the lightest configuration and gave us the best structural efficiency and all the control power we needed for maneuvering," Mullin explains. "The biggest consideration was its light weight. Weight drove the decision."

"A diamond wing has more square feet of surface area, but is more structurally efficient," adds Renshaw. "The longer root chord provides a more distributed load path through the fuselage. Multiple bulkheads carry the bending loads. The design provides more opportunity to space the bulkheads around the internal equipment. It also provides more fuel volume."

"The structural engineers wanted a diamond wing because it provides a larger root chord, which carries bending moments better," Hardy notes. "The aerodynamicists wanted a trapezoidal wing because it provides more aspect ratio, which is good for aerodynamics. Dick Heppe, the president of Lockheed California Company, made the final decision, and he was right. The aerodynamics were not all that different, but the structure and weights were significantly better. So we went to a diamond shape. The big root chord, though, moved the tails back. Eventually we even had to notch the wing for the front of the tails. If the tails moved farther back, they would fall off the airplane."

Source: http://www.codeonemagazine.com/archives ... 2a_98.html