The visual impact of that tip alone should not cause cops to pull you over. Now if really loud fart noises are coming out of it and you're driving like a madman, you'll get pulled, but that has little to do with the size or your ehaust tip.
The SPT exhaust on my RS has a relatively large tip. I don't seem to get any extra attention from it.
Kind of off topic but I'm actually suprised at how little attention my car gets from the cops. It's like they can't see the hood scoop, big open bumper and tall wing. Must be a silverthorne thing.