Steve,
Not sure what you mean by "schedule" as the flight you are ready to PIREP is a Personal flight correct? The reason why you cannot file with the YS-11 is because it is a "large" aircraft category and is not valid for personal flights (at least the one aircraft that is in the database that is a NAMC YS-11). I would suggest filing the flight with another dual engine of your choice and put remarks in your PIREP regarding this issue.