The impression I have about FFP it is that it was not achieved 30+ years ago it is that no one thought it would suppress bremsstrahlung radiation with the magnetic field in the pinch. But after Lerner posted the idea a few years ago on the net, it would be very trivial to achieve that. Much easier than even design an atomic bomb or a ICBM, even if it is a fluke lauch. So, I dont think it is hard to imagine NK with a FFP.
