I spent many hours after the installation of my Stillen CBE onto the NISMO and had plenty of frustration with fitment. If you are having issues with fitment, this will hopefully shed some light.
I had the left section of exhaust hanging down after repeated fitment attempts. After unbolting everything and fitting piece by piece to find where the problem was I found that there an additional bracket on the left side of the muffler section that was not welded but bolted on to the vehicle. The exhaust hanger will strike and create a good bit of tension with this bracket in place. You need to remove this bracket!
There is a 12mm bolt holding it, just take out the bolt and the bracket will be free to work with.
Once the bracket has been removed from the vehicle you can then remove the rubber hanger by unfastening the 12mm bolt holding it to the bracket itself.
You are then left with the hanger and two 12mm bolts, 1 short/1 long. Use the longer bolt to re-attach your hanger.
Your new placement of the hanger will go where the shorter bolt originally was.
DONE!
I am not sure why anyone including Stillen has been faced with this issue yet but I did not see it in the instructions and have not found any postings about it, hope this saves some un necessary bending of anything.
Good Luck!