Please don't consider me an expert on composition, but with a pattern like this, and the fuzziness around the perimeter you were going for, i think the focal point in the center is the right approach. Also, the exposure is great, so I don't think flash would have helped..it probably would have blown out those beautiful delicate highlights and introduced more contrast. I think it's a great shot. Am looking at getting that same lens myself, so work like this is good to see!:
