We will be taking the train to Sapa in late March. I have two questions:
Is there enough room in the compartment for four- there are two of us only but there will be other people- for two suitcases 24"x 13x9?
Are the bed linens clean or should we purchase a liner in Hanoi?

Hi Zinfanatic,
There are many nighttrain to Lao Cai : Victoria, Ratraco, Royal...They have both the compartment for four and for two persons. But For two is more expensive.

There is room under the bottom bunks for suitcases and yours aren't huge so I think you should be okay.

I felt the linens were clean enough and I slept in my sweats anyway. Whether or not you bother with a liner is up to you.

I really enjoyed SaPa!

You won't need liners with the Victoria train. The suitcases would fit under the bunk (2 suitcases under 1 bunk).

We took the Livitans train in October and did not feel the need to use our liners. There was additional baggage storage over the door for large cases. The compartments are pretty compact but we were sharing with friends and the coziness didn't bother us. We slept most of the way in both directions.

My advice will be: leave the big bags in your hotel in Hanoi and then you don't need to worry about them any mote.
They provide, on the train, with pillow and blanket, however, people still prefer to bring their own sleeping bag which can be bought in the Old Quarter of Hanoi for around 15$. Hope this help.
Happy Travel