a little late to the thread but I tried it first hand, I didn't know what brand it was, I wanted to see how the car will feel with more downforce at the back, and this was the only option I could borrow from a friend.
To make it short, it didn't help a lot, I got a slight drop in my top speed at track (around 3 mph drop compared to oem spoiler), which means it provides a little downforce but not to the extent that you feel it in turns. I returned the oem spoiler and will get some proper aero in future.
The only good side, it goes well with car lines.
AlWakRa 370z's Journal - PW from Qatar