I've seen some discussion of the possibility but wondering if anyone has every done it. I'm entertaining the idea of drilling a hole in the cast wheels for an inner tube valve stem. I would like the option of putting a tube in a tubeless tire if I were to get a hole or cut too big to fix with a plug or if I get a hole or cut in the sidewall from a sharp rock on the trail. The valve in the spoke of the cast wheel prevents this option.