Hiya guys -
I didn't invent this, but stumbled upon it somewhere. But the improvement, at least for me, was so profound that I thought I'd repeat it here lest it gets lost in the mists of Internet.
If you're finding your Huey twitchy and/or oscillating along its longitudinal axis even after applying JS curves and/or reducing saturation, try to increase your rudder sensitivity next. I set mine to -20 and the difference is like night and day, the chopper is rock solid now and doesn't gyrate along the roll axis anymore. Try it if everything else fails, since coordinated flying is much easier if the rudder is more responsive I've found!
Thanks all and report back ;)