Much of the information passed back by FTP is dependent on the server implementation (and config). There is no standard what should be a directory listing (and in which oder and which units).

If a server doesn't send file sizes back, you won't get them, and there's nothing Net::FTP (or any other module) could do about it. Period.

Of course, first you should check (with an interactive client), what you do get back from the server. That might be interesting for your other problem, too.