Thanks for the replies :)
First of all; I'm not recommending this to anyone ;)
Second; I ride Crow with all kinds of bits and bitless as well, and I don't agree that a snaffle has more control than a bitless. A severe bit or bitless might give more control, but only in situations where the horse doesn't listen because he finds you unworthy to listen to, not when he's afraid or scared. I agree that this particular version is less able to control the horse vs a snaffle or other bitless, but that's also why I got benefits from it :)
I didn't have any problems at all after the first 15 minutes when Crow and I figured how to communicate without my constant corrections in the left or right rein. Last time I tried, in march, we didn't get it to work tho. And I take that as a proof that my riding has become better, in my point of view nd to my goals.