Hi,
As far as I understand your query, it seems that you would like to make changes in the guest customization once the clone API starts processing the customization and before it actually completes. This is not possible to do. Once you have submitted the customization spec to the Clone API, there's no way once can modify the same when the VM powers ON. After the power on,all the customizations take affect and get applied to the VM.
I would like to know your use case here of trying to perform this modification.
