Does anyone know why the roof of my 2014 non z51 corvette stingray coupe is heavier than the roof on a 2014 corvette stingray z51 coupe model? My husband has the stingray with the z51 package and his roof is noticeably lighter when compared to my non z51 roof. They are both made of carbon fiber so I'm wondering why mine is so much heavier? Has anyone else noticed this difference? Why do you think this is?