Although these will extend beyond the edges of my 88 mm skis they seem not to have been made for such wide skis and the friction of the ski plus any icing often causes them to fail to engage. Many is the time I've stepped out of the bindings to see skis with brakes that didn't pop down. Also, they are not as heavy and aggressive as some brakes so the ski may still move when the brake is down but the snow is soft/light and the slope steep. That's the conditions we bought these bindings for, right?
I like my Dynafit bindings and the company was cool about hooking me up with leashes. I would recommend leashes for these bindings. Ski brakes won't help you in an avalanche, so if you are going to go where you really shouldn't go, just unleash. If you are crazy, lock the toes down. Maybe you can ski out that avalanche, you wild fool.
I got leashes after almost losing a ski in deep powder in the backcountry. It would have sucked. The ski released prematurely because I failed to notice ice in the holes in the toe of the boot, preventing the toe from being properly engaged. An easy problem to solve, especially if you use the Dynafit leash which has a handy little tool for that purpose.
Take a careful look at your toes and memorize what they look like when they are fully engaged so you will recognize when they aren't.