Ford's sales force recognized the threat and advised Henry to respond to it. Initially he resisted, but the T's sagging market share finally forced him to admit a replacement was needed. When he finally agreed to begin development of this new model, he focused on the mechanical aspects and on what today is called design for manufacturability (DFM), which he had always strongly embraced and for which the Model T production system was famous. Although ultimately successful, the development of the Model A included many problems that had to be resolved. For example, the die stamping of parts from sheet steel, which the Ford company had led to new heights of development with the Model T production system, was something Henry had always been ambivalent about; it had brought success, but he felt that it was not the best choice for durability. He was determined that the Model A would rely more on drop forgings than the Model T, but his ideas to improve the DFM of forging did not prove practical. Eventually, Ford's engineers persuaded him to relent, lest the Model A's production cost force up its retail price too much.