be careful that when restoring the root/opt combo you need also the same kernel of the original backup otherwise the device can and will bootloop. This, because if you need to flash your device prior to restoring it, remember to flash the correct kernel as well or to install the KP kernel if you are using it. Now it's too long a time I'm not doing it anymore (reflashing) so I am not able to remember all of the details, but that's the concept.