The plastic will break down over time in the sun, I am surprised you got 6 years from that! Its a sad day when you have to remove mods that have defined our cars for so long
if you liked the rough shape, put it back on the car after putting was paper on the car first and you could use the old one as a template/ mold to fiberglass a new one. That is what I did to get a good seal between my Matrix and its tail.