I put ATA drive at the top of the Boot order in legacy; UEFI Boot sources don't include any ATA drives, just USB CDROM; Enabled QuickStart
I have restarted Snakeoil and the USB hasn't prevented boot. So far its looking good.
That comment Agent Kith about persistent LiveCD - I don't have the ability to set up any OS with USB, it has to be CDROM.