Hi,
Long time reader, first time poster.
I recently decided to stop booting from, and writing to, the usb flash drive after two drives has gone bad. There seems to be some information on how to do this, but I could not find any method that was simple, clean, persistent and "set-and-forget".
I solved it by overlaying bzroot with a tiny initramfs and wrote up all instructions on how to do this here: https://github.com/thohell/unRAID-bzoverlay
This will also work well when running unRAID in a vm where boot from usb may not even be possible. No need to chain load using plop or other hacks. Just build a small boot image using these instructions.
Hopefully this information is useful to others.