FYI -- I am working on this a bit, too, and I found I go much faster with a larger wave and fewer kicks. I repeat 18s w/24 kicks or so and I'm around 20s with my fast kick, which is 30-34 kicks. My best is 16, always at the end of practice.
YMMV, and I have small, inflexible feet feet. And, I have no idea if these times are good.