Hey Joe I have the Wilkinson GTS mufflers.
You cant talk next to the car rear when its idling but they are not bad inside the car. No issue when driving - great sound.
The Wilkinson GTS rear pipe measured in at 2.5 inches diameter and the header offtakes at 2 inches diameter.
The eyeball joint between the headers and exhaust assembly is a fantastic addition. My car previously had a full 2.5 inch header collector and a modified rear exhaust set up on a fixed flange. It was pretty well impossible to get the twin exhausts straight and level and miss all of the suspension interference and rub points. Consequently I had two or three suspension rub holes in the old exhaust when it was pulled . With this setup you can get it pretty well spot on and clear everything using the standard mounts.
Looking at the suspension clearances it is close to the maximum possible without getting contact when the suspension moves.
Just be aware when you start it up for the first time half the paint will burn off the exhaust collector painted end pipe ( which also looks like stainless underneath ) making one heck of a lot of smoke ! The shop should do it outside !
In my view a good performing high quality product that fits really well. You don't get to say that too often.