You'll need two slashes as far as I can see. The first is required as otherwise there's no possible way for the Uri class (?WebRequest) to even know where thehostname part ends! :-)
After that you should likelyleave in the '>' characters. You'll (likely) need the second slash so the FtpWebRequest know where the filename starts, e.g. with
ftp://host1/path1>path2>path3/file.txt, it will connect to host1; CWD to "path1>path2>path3"; and RETR for "file.txt".
Hopefully it doesn't do anything too odd with the '>' chars... but it might...
Turn on network logging to see exactly what FtpWebRequest sends. See
http://msdn2.microsoft.com/en-us/library/ty48b824.aspxand/or
http://blogs.msdn.com/dgorti/archive/2005/09/18/471003.aspx
http://www.alanjmcf.me.uk/ Please follow-up in the newsgroup. If I help, mark the question answered