How can I set application custom properties with the Orion SDK?

This might be an easy one, but I am getting an error when attempting to set SAM Application Custom Properties with the SDK.

Basically, I'm following the example for setting custom properties for nodes, but I'm replacing node-related information in the URI with application information.

Here is the resulting URI, which I'm guessing is invalid: "swis://my_orion_server/Orion/Orion.APM.Application/ApplicationID=replace_with_application_id/CustomProperties"

Simplified script:

$hostname = my_orion_server

$appID = app_id_of_interest

$swis = Connect-Swis -Trusted -Hostname $hostname

$customProps = @{ Comments="Custom comment"; }

$uri = "swis://$hostname/Orion/Orion.APM.Application/ApplicationID=$appID/CustomProperties"

Set-SwisObject $swis -Uri $uri -Properties $customProps

Error message: "Entity Orion.APM.Application is hosted by entity Orion.Nodes."

Thanks in advance for any help!