If you hardmod and patch from 11.0 cubic ninja will work...If you have a hardmod, 11.0 is downgrade-able. However, you still need access to homebrew, which the only current method is to either use supermysterychunkhax or wait for ninjhax/browserhax/oothax/any other entrypoint to support 11.0.
You don't have any NAND backups, do you?