I've played this game since I was little. I personally don't play the slug backs. Most people don't seem to have heard of two hits for a convertible, so I get to do lots of smacking on those. All three of my girls play it too...and yes, we play with the new ones.
I had no idea what "Slug-backs" were when I first came home yesterday..aggrevated and determined to find a "Slug-Bug Manual" online. Can you use vehicles that are parked in parking lots, that you drive by?
And what about the bugs that are on service roads (feeder roads)??