2011 Shelby GT500 exhaust tips - any suggestions?

While nice, the existing 2011 Shelby GT500 exhausts are almost invisible, due to the fact that they are not dressed up with fancy exhaust tips.

I'd like to rectify that by adding more visible exhaust tips. This car deserves exhaust tips which speak to its raw power.

That said - any advice for some bolt-on exhaust tips?:

1) Inlet width - is it 4", or does it have to be bigger?
2) length - I've found some that are 12" long end to end, that's the shortest I could find. Is 12" too long? I'm thinking something 1-2" longer than the existing tip is good enough.
3) style - I like the style of the "resonating exhaust tips" as they are better looking and have more visible surface area. However, I don't want to change the sound of the exhaust into something undesirable. What are your thoughts?

Thanks!