What size tires?

I have a set of Varrstoen ES1 18x8.5 on my TL, which currently have 225/40/18's on them. The tired are stretched with this size. I am lowered (but not slammed) on Function and Form coilovers (hoping to upgrade to Tein soon). The ride is currently fairly rough and I'm not sure how much the tires being stretched is impacting the ride quality as I bought the car with this setup on it. This is the first time I've had stretched tires on a car, but I assume the stretch makes the sidewall stiffer, which may be contributing to the harsh ride.

I don't really love the exposed rim look of the 225, so am looking into getting a 235 or 245. Will this improve the ride quality much? Could I have any rubbing issues with either size? Should I stick with a 40?

Thanks!