A bit of a peculiar question, but I figured this would be as good a place as any to ask (it's for something I'm writing), given the wide variety of experience here.

So: WWII. I'm given to understand that a 'bed' in a submarine is a 'rack' rather than a 'bunk'. Now, if several men were in their 'beds', how would it be phrased:

1) they are in the rack;
2) they are in the racks;
3) they are on the rack;
4) they are on the racks;
5) they are in/on their rack;
6) they are in/on their racks:
7) some other way?

Any help appreciated. And don't worry; I'm not going to be writing as an authority on life in a submarine; I just like to get things right.