Hello,
there is a way to set FtpProxyType. The FtpProxy class is actually a child of Proxy class so you can set it directly the following way:
var proxy = new FtpProxy();
proxy.Host = "host";
proxy.ProxyType = FtpProxyType.FtpUser;
fileTransferClient.Proxy = proxy;
Or the shorter way:
fileTransferClient.Proxy = new FtpProxy(FtpProxyType.None, "host", 987654, "username");