ModelDoc2 OpenDoc6(

   string FileName,

   int Type,

   int Options,

   string Configuration,

   out int Errors,

   out int Warnings

)

Options:

swOpenDocOptions_RapidDraft    8 or 0x8;    Convert document to RapidDraft format (drawings only)

What's the meaning of  the "RapidDraft format" of drawings?