A lot of people are complaining that this will be the 29-29-29 plan before long. Any tax plan is subject to increases.
You can worry about 9-9-29, but not 20-20-20.
Actually the Laffer Curve would prevent a 9-9-29. At some point you would tax consumption to the point of reducing revenue. What the true number is depends on how much economic activity results from the other two numbers. If the economy is going gangbusters and incomes rise then spending is likely to rise up until the price no longer justifies the expenditure. That would in turn affect sales and I can guarantee corporations will be concerned with falling sales.
They are all linked together, we already pay higher prices by way of the corporate tax (a cost to production). This just makes the entire cost of government transparent.