Cessna fuel selector - bad idea
In a low wing aircraft with 2 wing tanks you should (must?) be able to select each tank in turn. As the previous post mentioned, if both are selected and one empties, the engine will suck air until you select only the tank with fuel in it. It doesn't matter how you uncover the fuel pick up in one tank (slipping, flying upside down, etc) the engine won't start drawing fuel again until both pick-ups are covered. IMHO poorly thought out fuel system modifications result in many engine stoppages. Why not stay with the simple, tried & tested system Van's recommend? Changing tanks every hour is not really a hardship. The only change I have made is an Andair fuel selector.
Pete