Go for it!

The scale works for your size table, so don't over-worry about the shape. Love this fixture!

I think the fact that it's longer one way than the other will look awkward. With a 54" table, that means the longer dimension will be only 8" from the edge of the table at two points. I love the style of fixture, and I'd suggest you look for one that's not as elongated. I think an important factor is how high above the table this will be mounted. If you have a high ceiling and the fixture is well above a person's height, then you might be able to manage this. If it hangs lower, then it's within head-bumping range when someone sits down near the wider dimension. This is awkward to describe, but I hope I've been clear!