Why does every think just because we say "large wheels hurt your performance" that what we really mean is "your dumb for having large wheels"? The other main factor in "real world" tests other than PMOI is the tire it's self, and that is to hard to make a constant in real world testing. Even in JohnC's test, if they were the same model and brand, they could have different compounds affecting traction.
I like to think HybridZ runs on facts. IF you have 18's because you like the look, good. If you have them because that is were the selection of tires you want are, fine. Just call it what it is.