I would go even a step further, if all work is result driven, why having work hours anyways? Why not just agree on what has to be done in some future time period, and forget about hours completely?
That way, employees will feel more relaxed, and accomplish more.
I'm sure I can do more in 20 "high hours" than in 40 "forced hours", but if you don't let me work only 20 "high hours" a week, and assign me 20 more "forced hours", it would inevitable lead back to 40 "forced hours" with much more work and less done.
That's why I never bid based on hourly rate, but based on some agreed amount of work, when doing contracts.