I'm sure that if the tyre was proper odd looking then the coppers will act. A simple tyre wall/width difference should not be on their radar. Personally, i think the cars look nice with a slight stretch, but not some of the crazy stretched tyres you see on some forums + pictures. The people driving these type of cars are mostly always into cruising and not heavy hooning, so i would imagine as there is no hard evidence that this type of thing causes mass carnage and fatalities, then it should be up to the discression of the police how to deal with each situation.