My tires are a little over an inch smaller in diameter but I do that on purpose for autocross. My gearing tops out right at 60mph in second, it makes my acceleration marginally faster than OEM tire size. But you can always put on -1 tire size to keep the oem gearing.
I dropped about 2 inches with the ground controls. Any more and I'm killing shocks. If we can't afford a new race shock and spring setup I'm going to have what I got corner weighted by a pro... I guestimated. But its working out pretty damn well.
How does it effect handling? Let me put it this way, with just the wheels, tires, and ground controls I am faster than my peers that I ran against last year when I was stock with race compound tires. Matter of fact one guy who was hanging real close to my times in his scooby last year on street tires, switched to r compounds this year and now I'm even further ahead of him on average. Its all in the center of gravity and the killer alignment I got from our alignment shop of the gods.
Oh but if all you do is street driving you'll think ground controls are the worst thing ever. Linear springs, no dampening seals, metal tophats... if you ain't racing they will hurt.