Thank you for the great article. It works for me if I ask it to prompt for login and I give my credentials. But if I use the service account that has sysadmin privileges I get an error like this:

An error has occurred during report processing.

Cannot impersonate user for data source 'DataSource1'.

Logon failed.

Logon failure: the user has not been granted the requested logon type at this computer. (Exception from HRESULT: 0x80070569)

Also if I use my credentials the authentication is not passed down to the smaller reports - it only works on main performance dashboard. Any suggestions much appreciated, thanks.