Zpirate- the diameter is 19.6mm for ryan's. this is over the CF part of the housing.
The NRG i have on my G is smaller but only marginally... like 18.0mm. the car needs more like 10mm additional clearance for the dampers if it was not to rub the battery cover surround piece... there is just no room.
the structure of the 370Z is completely different from your 350Z and my G35C... there's really not much room in there~.
