I own a lefty/righty helle's belle, and I must say, those knives move so well, so effortlessly.
I train with all my knives, familiarizing myself with their nuances. Some require more muscular effort on my part, some less so.
My custom belles move better when I put in as LITTLE EFFORT as possible. Less effort, the more it flows. In my opinion, it's a true martial blade in that it really makes the practitioner flow and relax. Muscle it, and you're missing the point.
Might have to give Bill a call again. Talk Damascus with the Master.