Romad, regarding your larger aspect ratio tire question, here is a link that will provide additional information for your consideration. There are limitations to improve the ride. Certain shocks, tires, but the short coupled Crossfire is the major reason for the wash-board ride (depending on the surface) Keeping your gas tank full increasing the weight also helps. (A gallon of gasoline weighs roughly 6 pounds). Keep in mind it IS a sports car.

wheel_stuff(1).xls

(Click the 'skip sign in...' then close out the Mico-soft banner page and you have full view of chart)