I make two systems for this car. The 7"diameter(178mm) is the same diameter as the Lotus Stg3 exhaust - so same sound but without the dronnnnne. .
The larger 8"diameter (203mm) is quieter (but still has a great scream) and may be best for prolonged motorway driving or countries like Switzerland where you need to be careful with NOISE. The 8"diameter is recommended for trackdays at most circuits.
Choice of factory oval tailpipe or twin-tip layout.