If you can put other crew members that are rested in the seats, do it and get your sleep on the jet. Otherwise, you are taking a chance that I know you friends, family, and the leadership wouldn't want you too --- not to forget the people you fly overhead, the passengers, and your crew members family and friends.

If you are that tired, call crew rest. Plain and simple. If your mission or cargo was that important, you would have had a spare plane and crew. But it isn't so don't kill yourself.

-Fatty