Within a container I use a script task to verify the file
eg.
Dim FileInf As FileInfo
FileInf = New FileInfo(Dts.Variables("User::FullFileName").Value.ToString())
Dts.Variables("User::FileSize").Value = CInt(FileInf.Length)
and then depending on the filesize set a status flag, which I then use a precedence constraint outside of the script to select the component output flow as per diagram.