I had muscle pains for about a week when i first got it. you have to give your body time to adapt to the new (and better) seating position. My aches were on the shoulder/arm area. I am 6ft too. They also went rather quickly
the guy is asking if there's any difference in shape between a Nismo spoiler and a replica spoiler.
they are both made of FRP (well the Nismo JDM and the replicas) and to have fitment issues it should be a really bad replica tbh.
Once painted you shouldn't be able to distinguish the 2