All of what you said it true, KimJapan.

I've already figured out that I will need to return to Vietnam. It is a good thing that weatherbase shows that Hue has 25+ inches of rain in November. That removed Hue and Ho An from my travel options for this trip.

The day trip to Halong would give me more time to spend on Sapa. IsisMnroe's vote carries some weight.

I believe that my timing is right, weatherwise, for visiting Sapa. I can't get the Vic Xpress trains but can get the wood cabin in the Tulico car.

Arriving SGN at 10:20PM, staying that
Saturday night in HCMC.

This would be my lodging itinerary:
Nov 4 arrive SGN 10:20PM, night in Saigon.
Nov 5, Saigon
Nov 6, Hanoi
Nov 7, day trip to Halong, night in Hanoi
Nov 8, see Hanoi, 10PM night train to Sapa
Nov 9, Victoria Sapa
Nov 10, Victoria Sapa
Nov 11, day train, night in Hanoi
Nov 12, Hanoi or Saigon
Nov 13, Saigon
Nov 14, Seal Beach, California

I stayed overnight on a boat on beautiful Halong Bay and still look back with longing on that absolutely perfect night's sleep and the lovely sunrise/sunset. I can get seasick in the bathtub, so I was a little concerned, but it was marvelous. I did feel that the one night was enough due to my limited time, and I was a solo traveler with mostly French speakers on board, but it worked out very well.

(As an aside, be sure that they know you're solo...When the time came for sleeping, we found that they had assigned a Vikingesque Aussie guy and me to the same room; he kindly agreed to sleep out on the deck. He was a great guy, actually, but the acquaintance of one day...well, let's just say it would nave been a bit too cozy.)

I got a reply back from Handspan and they have availability on the Dragon's Pearl for the overnight on the 7th. I've swung back the other way and will probably take that on the 7th, back on the 8th. Night in Hanoi. Day train to Sapa on the 9th. Night train on the 11th. Something like that.

I did notice the single supplement fee!

Last November I have done a day trip from Hanoi to Halong, with private transport. A reasonable early (not nightly) departure, even a few short stops along the road to walk around rice paddies where people were working, and then a five hour cruise. Return to Halong in the evening, part of the trip after sunset. It's perfectly feasible. And a cruise of five hours in Ha Long is enough, I think.

The overnight trip with Handspan on the Dragon's Pearl was great. Am definitely glad I stayed over. It is a long trip getting there and back. It was an excellent relaxing break from crazy Hanoi. Might have stayed over another night for some kayaking if I had that option, but not enough time.

There are rats here in the business class lounge at Hanoi airport.

Glad you enjoyed the Halong Bay trip! How was the weather? BTW, no rats (that I saw) at the train station.... Did you go to Sapa?

It was hazy at Halong Bay and a bit cloudy, but this was good. Was warm and would have been quite hot in the sun. Nice breezes in the evening and it was comfortable all day long. We visited caves on the second day that were fairly spectacular, much more extensive than I imagined.

The food on the Dragon's Pearl was very good as was the company there. The crew was very good. As I said, I got the tour via Handspan. Our tour sub-group was two Brits and me. Our guide, Sunny, took very good care of us.

Sleeping on the boat was easy. There was an air conditioner unit in the room but it was not necessary overnight. The boat anchored in a bay with about 20 other boats. It was quiet and the water was dead calm.

Unfortunately, I did not get to go to Sapa. Had to shorten my trip by two days and that squeezed out Sapa and made it easier to decide on taking the overnight trip to Halong Bay.