understanding how the rockers work, i think thats a bad idea. the pressure from the shaft pushes the rocker arm down and away from the shaft. basically the push rod and the valve tip are pushing on the rocker arm in the same direction and forcing the bottom of the rocker pivot hole against the bottom of the shaft. the direct oil is designed to create an opposing force directly where the peak pressure on the joint is and this area is force lubricated. if you flip the rocker shaft around and the oil holes are pointing up, then thats the area where the most clearance occurs between the rocker and shaft and the oil is allowed to leak out past the rocker and oils the fulcrum point very little. hopefully this explanation makes sense. if not i can post a drawing later depicting all the forces on the rockers and how the oiling design counteracts them or at least lubricates the critical areas.