In 2000 I bought a flat stock appearing fiberglass hood for my Challenger from AAR. I planned to cut a hole for a tunnel ram but noticed I would be cutting thru the underlayment structure. A gentlemen at AAR told me to place hood upside-down on a blanket or lawn/grass. Then cut slabs of styrofoam insulation board like Celotex and fit them into and in between the existing structure. Then lay fiberglass cloth over the foam board. After it cured I cut my hole and the hood remained uncompromised and stiff as can be.