@Anonabhar The NAUbackup script goes in order of a list of VMs, so I can imagine it'd be easy to implement this if not already present in XCP-ng. Worst case, separate those big VMs out into a separate backup instance and offset it adequately from when the other backups run.
@olivierlambert Ah.. I'm being thick.. I didnt have the plugin loaded so I was wracking my brains to try and find out where the hook would have been called.. Thanks for you help, and back to coding! 8-)