This weekend I saw a bit/bridle setup that I had never seen before (rated show in the hunters). Standard caveson bridle with regular noseband going all the way around. D ring bit, no hooks/slots (not a mylar). Curb chain. It was a little hard to see, but I believe the burb chain was attached to the top of the bit hangers on either side, where they hook over the bit. Single set of reins attached typically to the D ring bit.
How would you even engage the curb action directly?