Thanks, kings10!
I've seen aftermarket rims similar to the black rims that came with the performance package in 18's, I may have to go down a size then and look more for touring. I was on an Ecoboost Mustang forum and there seemed to be a general dislike of the PZeros and people were swapping them out.
Also, I just found that unless the Pirellis get hot they just always seemed slippery. This is the 19's the car came with, rim style: