The company's design team quickly projected that a low-wing monoplane design would be capable of delivering the desired level of performance sought; other features were to include a fully enclosed cockpit, a variable-pitch propeller, and landing flaps. It was decided to submit their own response to the requirement, designated as the "M.S.405"; work on the design was headed by the firm's Engineer-in-Chief, Paul-René Gauthier. Both the shape and basic configuration of the M.S.405 were hotly contended, particularly between 'traditional' advocates of biplane aircraft and 'modern' monoplane supporters.