Seems to me it has to be the same as current progressive rate calculations. You are taxes 1% on the first 30000. 5% on the next 70000 and so on. Seems like that would need to be consistent with his plan for the very reason you mention.
How about charging everyone 10% at the federal level and 10% at the state level with the total tax liability for any one individual or corporation no more than 20%?