Version 2.02 of powerdown is available. A directory on the flash drive is now available for your custom shutdown scripts. The directory is /boot/config/plugins/powerdown/custom/. Place any script files you want processed at the beginning of powerdown. The files should be named Kxx - where xx is 00-99.
For those of you running VMs, you will need to provide a custom script so powerdown can shut them down before unRAID tries to stop Xen. I know you'd rather just have powerdown do that, but powerdown is being kept generic for both v5 and v6 (plain vanilla, and Xen). Because each user has unique needs, this is the best way to handle the situation.