Thank you, everyone, for the replies and first hand experience. I was relying on the same info that Christep quoted. Booked and paid for hotel and ferry based on that information.

I guess I will take the afternoon flight to Hanoi. Didn't really want to waste so much time, but being able to sleep in may be a benefit. 11:00AM ferry to HKG and 2:00PM flight to Hanoi. Kind of shoots much sightseeing that afternoon. Thanks again for the info.