I used a hacksaw blade and rasp to form the foam. To get under the existing fiberglass, I used a dremel with grinding bit to create a undercut for the fiberglass mash.
As it stands, one layer of matting and many more to go:
Next steps are to use fiberglass weave fabric (Biaxial) and continue to build up. I'll post more in a couple of days. Only time I can work on it is before work at 6:30 AM. Neighbors must think I'm nuts.