Depends. If you're using it offroad you'll probably hate it. If anything you'd want WIDER bars to increase leverage and control of your front end and reduce rider fatigue through the rough stuff.
The primary reason sportbike bars are narrow is to reduce your frontal area, a neccessary evil for going fast. They'd all handle better with wider bars. This, combined with steep steering angles is why they're so twitchy at low speeds.
But if you just gotta have 'em, looks like stock bars could be narrowed about 1 1/4" per side before you ran out of room for your controls and mirror perches.