Well, the "spirit" of your argument is: "When taxes are down to 3% flat (across the board for fairness sake) the GDP is going to increase so significantly that 3% should cover it comfortably ! :)"
GDP would have to TRIPLE for your "spirit" to even be in the right neighborhood.
NNNNNNNNNOOOOOooooooo !!! The SPIRIT of my argument is you can raise productivity AND tax revenue by lowering tax rates! The numbers were thrown in just to make a point!