Brainwaves are simply electrical energy operating at frequencies of about 0Hz to 40Hz (roughly), and I think FWS is pumping in 15Hz, which is low beta range, which is the high end of the sensory motor range, possibly accounting for an increased bodily relaxation. But it sounds like there's more than just that going in, though I really have no idea how the thing actually works, lol. The overall point I was making was not really about the frequency per se, but about the fact that, whatever frequency (or frequencies) it's using, it's pumping that into the brain artificially, like ECS (electroconvulsive shock therapy), albeit on a much, much milder scale. Whereas with EEG neurofeedback, nothing is pumped into the brain at all, but instead your brainwaves are merely read by the equipment and then that information is fed back to the brain, so the brain can then make its own adjustments (e.g., raising alpha, lowering theta, or whatever you're trying to do).
Not that that might not have risks, too, but overloading a delicate CFS brain with outside electrical energy wouldn't be one of them. Although in some cases (like yours, apparently) it seems that artificially zapping the brain with whatever electrical energy the FWS uses has had a beneficial effect in correcting something, which is what makes it interesting to me. Maybe all of our CFS brains might need jolting, in other words, like to "wake up" the HPAA or break up some coherences that are keeping the CFS locked into place. There is a form of NF that I think some people have talked about here, called LENS (Low Energy Neurofeedback System, which aside from the neurofeedback aspect also shoots electricity directly into the scalp/brain), but reports of that w/CFS have been mixed at best, I think. But maybe whatever FWS does is sufficiently different from LENS that it could actually benefit a lot of people w/CFS. It would interesting to have more reports of this with CFS.