Hello Sir!
It's nice to have another 370Z on the road in the UK. Maybe I'll see you at a meet or 2 this year
I think you'll find the boot is very close to the same size. I'll dig out a photo of the 2 mats on top of each other. The thing that restricts the size a bit is the roller for the cover - it sits within the boot area rather than over the top of the silver bar.
As you say, the power increase from an '04 350Z is very noticeable