Ive been lucky enough to make four JS-3 flights now.

On my last flight I found after crossing the finish line and entering downwind to land that my right elbow had bumped the water dump valve and it had sprung closed. Having the airbrakes detent was darn convenient to hold the brakes in place momentarily so I could re-open the dump valve, all while keeping my right hand on the stick.

The flight manual suggested a medium flap setting on downwind and going to landing flap on final. Being able to hold the airbrakes in place while switching between airbrakes and flap control is nice.

I will also note that so far I have come no where close to using full airbrake on this glider. The airbrakes are quite powerful.

As a side note - so far I have only flown in 15 meter configuration