How do I select a specific SSL certificate in FluentFTP?

Question

I'm connecting to a shared hosting site and the hosting company says it has a valid certificate, but I get a failure with FluentFTP. If I use Filezilla, I see a dropdown that lets me select "certificate in chain". Position 0 shows an expired certificate but position 1 shows a valid one.

How do I select the chain position in FluentFTP

My VB code for FluentFTP is

ServicePointManager.ServerCertificateValidationCallback = New System.Net.Security.RemoteCertificateValidationCallback(AddressOf AcceptAllCertifications)
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls
        Using conn = New FtpClient("secure11.host", "user", "pwd")
            conn.AutoConnect()
           'do something
        End Using