You know what else is rough about this thing?
There’s nothing to push against. With the viola, you can feel the strings and the bow, and the reaction of the instrument feeding back into your arm. There’s friction. With the piano of course you’re pushing levers around, and they have weight and resistance.
With this thing, there’s no resistance. It’s like balancing in the air — if it were a hydraulic system, I’d say that there was no back pressure. That’s severely challenging.
On the good side, vibrato is a snap and a half.