NuMetal?

Question for my body veterans. I bought this car from a Mopar enthusiast who supposedly restore many Mopars. I’m Questioning one thing though, he used NuMetal epoxy puddy around the perimeter of the rear windshield to cover up rust some spots. The rust didn’t reach the roof, but on the channel. It looks solid, but I’m timid about spraying epoxy primer over it if it isn’t going to last and/or bubble.

Has anyone tried Numetal, and should I leave it, or go the hard route and cut it out and weld strips in?