Steve, the Bore size is 3", we have one customer with the Chargespeed rear with the TP17 option, so I'll make contact and see if he can supply a photo to us...
Good time to buy a Cobra as per my post here - http://www.350z-uk.com/topic/72098-cobra-exhausts-price-increase-due-soon…/#entry1074882
Let me know if we can help...