set vCloud Director vApp VM memory and hardware with PowerCLI

I am trying to modify the memory and CPU allocation for a vCloud Director vApp VM. The vApp is deployed, but stopped. I have tried various combinations of the PowerCLI commandlets, but with no success. My latest attempt, which looked promising, was this...

Get-CIVapp -Name 'VMName' | Get-CIVM | Get-VM | Set-VM -MemoryGB 2 -NumCPU 2

Has anyone found success in doing this?

Thanks

Paul