The /no_format_opt switch changes the way MIDL optimizes type and procedure descriptors.
midl /no_format_opt <other-options> filename
midl /no_format_opt mylean.idl
By default, MIDL eliminates duplicate type and procedure descriptors in order to reduce the size of the generated stub code. Using the /no_format_opt switch turns off this optimizing behavior.
General MIDL Command-line Syntax, /Oi