+1 on Dave's comment. Miel told me the top sprung valves were Dave's idea. I don't know if the short stroke was also Daves idea. The down side to top sprung valves is cost and length of the casing since you need room for the spring and guide mechanism above the valve and the same amount below. Making it a shortstroke reduces this somewhat. I think the cost difference may keep this from going into production.
I can say that the valve action is amazing...