I would usually run the board parallel to the mobile home floor joint. Mostly because this is most commonly the longest length, like down the hallway etc.
It also depends on how level the joint is. Sometimes I would have to sand the joint or something to make it more level.
You could also measure first so when you start, a full plank will strattle the joint, or just run the planks sideways.
You could run the planks at a 45 degree angle but this can really be a lot more work.
