I have a 95 Chevy Caprice. I wont to fiberglass the rear deck but the piece of carpet thats in the rear deck is in rough shape. I was wondering if i should just glass the carpet piece in the car then build up from there or make a one out of wood and go from there. Any help would be greatly appricated!!

Make new peice outta wood.
1/4" or 1/2" MDF.

It will be cheaper in the long run that using alot of resin on the carpeted part.