This was 'easy' Install image on uSD and do all the steps to make it bootable.  But instead of growing the rootfs partition, delete it. Install image on the sata.  Enlarge the rootfs and delete the boot partition. Insert the uSD and sata drive and boot. That is all it takes.  It helps that we dd the images so that both devices have partitions with the same UUIDs. There are improvements, like deleting partition 1 from the sata and moving the start of the rootfs to that point, but I did not try this.  I will leave it for others. Enjoy! But I really want complete booting from sata...