I have a few hatchery stock NH's that grew real big, real fast, as was their intent when they were developed. I was surprised actually given that hatchery consolidation has ruined most breeds. They were from a smaller hatchery though that is outside the midwest hatchery belt, so that may be the difference. I didn't process them however, as they are part of a breeding experiment, so I don't have metrics.
That being said, I simply wouldn't use NH's as a meat flock given that there are better options. They'll be somewhat serviceable if you happen to have them, but unless your primary objective is to improve the line over time, I don't see why you would bother going out of your way to use them.
Edit: The roosters can be, at times, a little cantankerous. Just FYI if that's a consideration.