Ahhh wait just a second . . . it is the LONGER the shot . . . so that holds true for ALL clubs regardless of loft. So for instance if you intended to rip a new one with your 9-iron you'll need to close it more.
So the harder you hit it with ANY club the more the clubface should be closed because the ball will be on the clubface longer.
Now you got it Bossman!
Just another tidbit...
The opposite holds true for swinging.