He takes care of the third 9 by always stating first that we need to get rid of the entire current tax system, which obviously includes repealing the 16th. More reason to ensure we elect a super-majority across the board in 2012.
Easier said then done and so far, he's not even saying it.
I think this is one area where Cain could improve. Being a Mathematician, some of these things he talks about are so rudimentary for him, that he forgets to break it down into simple and understandable terms. In the debate where he was talking Apples and Oranges with Romney, he tried to do that, but even Romney couldn't comprehend it.
It would be great if he could use a drawing board on stage and literally draw it out for the people who can't understand some of these concepts. Certainly the average Voter needs things spelled out in very simple terms.