Set Interface Thresholds with PowerShell?

Hello,

I'm trying to set thresholds on specific interfaces.

I am able to see the properties of the thresholds using Get-SwisObject.

$OutPercentUtilizationThreshold = Get-SwisObject $swis -Uri 'swis://orionserver.contoso.com/Orion/Orion.Nodes/NodeID=26/Interfaces/InterfaceID=270265/OutPercentUtilizationThreshold'

...but this set command is throwing a "Operation not supported on Orion.NPM.OutPercentUtilizationThreshold" error:

Set-SwisObject $swis -Uri 'swis://orionserver.contoso.com/Orion/Orion.Nodes/NodeID=26/Interfaces/InterfaceID=270265/OutPercentUtilizationThreshold' -Properties @{ Level1Value = 80 }

Is this a limitation of the SDK or am I doing something wrong?

Thanks!