No I don't think its all too necessary. It also just depends on what tires and what suspension you have. 9.5+38 with a 255/35 square is a very common setup ran by 3is owners.

 

I've been going through the wheel show off thread and some say it fits, others say it rubs if you take corners or have passengers in the back...

I don't want to order a set of wheels (especially at $1,200/rim) only to find out it doesn't work.

At first I wanted to go staggered, but the concave face 3 only comes with 18 x 9.5 +38 from what I was told. So 255-35-18 all around is what I would run on Falken or Yokohama tires.

 

Just a tip, you should post your wheels up on FR-S/BRZ/GT86 forums, you might have better chances there.