Using the following West Wind code to attach a file by the use of AddHeader()

loHeader = CREATEOBJECT( "wwHTTPHeader")
loHeader.SetProtocol()
loHeader.SetContentType("application/zip")
loHeader.AddHeader("Content-Length",TRANSFORM( LEN( cInfo)))
loHeader.AddHeader("Content-Disposition", " :attachment ;filename=" + cFileName )
loHeader.AddHeader("Accept-Ranges","bytes")
loHeader.AddHeader("Connection","Close")
Response.Rewind()
Response.ContentTypeHeader(loHeader)
Response.Write( cInfo)

Would there be any time processing factor if the attach file is about 400 Meg? I see this approach allows us to attach a file which is not among the IIS directory structure. Thus, we can send a zip file to the browser even if the file is not sitting in the IIS structure. If the time processing factor to create that header is not a factor then this approach could be used to avoid storing secure file in the IIS structure.