The Viltrix 16mm is on my short list, I missed out on a good price in my country from Amazon during their recent sales event. The CV15 is a small/light travel lens for when I'd otherwise not be carrying anything so wide at all. The Viltrix appears to be a great purposeful tool, with the size that often goes along with that.
Back to the Techart TZM-02, my curiosity is if it could be used for short in-camera stacks with something like a 55 micro nikkor or CV65. Some searching makes me believe this is probably not currently possible.