Hmm, from the bottom of that article I found this paragraph.

SQL Server Integration Services does not support the delegation of credentials, sometimes referred to as a double hop. In this scenario, you are working on a client computer, Integration Services is installed on a second computer, and SQL Server is installed on a third computer. Although SQL Server Management Studio successfully passes your credentials from the client computer to the second computer on which Integration Services is running, Integration Services cannot delegate your credentials from the second computer to the third computer on which SQL Server is running.

So it sounds like I can't do what I'm trying to do. The only way to manage packages in this configuration is to RDP to the SSIS server.

Bummer. :unsure: