I'm not going to SAY that would look terrible but I'm THINKING it.

 

 

Here's my biggest issue, the G35 is predominantly designed with sleek curves, adding a rear louver adds a lot of angular shapes and irregularities to the overall form and outside of a VERY FEW EXCEPTIONS it just really doesn't look good.

The very few exceptions usually involve substantial body modification like a wide body kit that already adds a lot of angular shapes, in that case the louver actually looks GOOD because it breaks up the sleek curve of the roofline.

However this is just MY personal preference, everyone has their own.

 

Search the forum; there is a thread with pics on this topic.