[Chebosto]

i have a 5 point rear roll over bar (weld in), cf hatch, but stock glass, pretty much the same setup as you Jet, but obviously not as powerful :P (but i probably have more carbon than you!)

i had the car corner balanced when i did my alignment. i didnt notice that much of a balance difference, the scales said i'm 53% front, 47% rear weight distributed, with me in the seat. car feels good.. during acceleration, probably would shift more to the rear, getting close to 50/50..

i would say lexan and cf hatch would be negligible for your z.