I like how you have kept that far left rock in the same place, that's a perfect positioning. I'm thinking you should really try some left-skewed or right-skewed scapes and see what you get.
I see of course what you mean about using an odd number of rocks to avoid a symmetrical scape; there is irony in the fact, however, that you've managed to make a very symmetrical scape using an odd number of rocks. Quantity's not related to symmetry -- arrangement is!
Whatever you do, do whatever works best for you. I'm not sure if I'm bothering you, but I feel like I am