What you would do is to shift the tax burden to the lowest income groups. As Adam already showed you, you would take nearly all disposable income from the two lowest quintiles.
PS...anytime you want to, you can overpay to your hearts content....I would expect you to, since apparently you think it is your duty to do so. Let us know about that, OK?
PS...you proved my point once again, a flat tax will create a greater wealth inequality.
"The necessaries of life occasion the great expense of the poor. They find it difficult to get food, and the greater part of their little revenue is spent in getting it. The luxuries and vanities of life occasion the principal expense of the rich, and a magnificent house embellishes and sets off to the best advantage all the other luxuries and vanities which they possess. ... It is not very unreasonable that the rich should contribute to the public expense, not only in proportion to their revenue, but something more than in that proportion."
-- Adam Smith