Like I siad, if your responsible and keep it under wraps you should be fine. I've had a paint ball "marker" in my back seat and been pulled over. It was cased and I was honest about it. I've walked into city hall and 1PP with my multi tool "surrendered at the check point of course ".
My point is keep a thoughtful head about you. Don't go to Central Park and target practice on the main lawn. Don't carry your Xbow over your shoulder while walking around in the financial district.
I think I would go ahead and print out and laminate the safty certificate and carry it with my bow. There are lots of archery shooters in the city and five boroughs.