I have a question about the fiberglass insulation under the hood.

Most of the cars I've owned, the 'glass matt is long gone.

But.. the 87 chevette I got is completely stock. It has five bad spots on the paint in the hood. They looked suspicious to me..

well today I got to work on it, and have concluded the rust came thru from the bottom. I suspect the 'glass mat got wet, and held the moisture against the hood. The paint on the underside of the hood was never intended to fight long-term moisture.. and in five spots it ate thru the paint, then thru the steel.

Well, I got the matt off in one piece, and it's in great shape. But I'm not sure I should replace it. I took a grinder to the worst of the rust, and shot some primer over it. Will get some grey paint to cover the primer, but the rust isn't 100% gone, and I am thinking the hood would be better off without the matt.

What do you thinK? replace the matt or no?