keyser, all I can tell you is that all of my testing has never proved that center weighted clubs will apply more energy to the ball. I have done hitting tests and laboratory tests with high speed photography and force analysis progarams and again nothing like this has ever showed up. I would also assume that a touring professional would pick up something like this if there is a significant difference and they would all be playing muscleback irons. Truth is that perimeter weighted irons perform best for 98% of all tour players. The muscleback is almost gone from the tour. Tiger will probably play his forever because they work for him.