mobileortho
I don't have much confidence in glue as a permanent fix, especially if it will be working in a vibration zone. I can only tell you what I would do in your situation. I would buy a cheap mig welder and learn to tack weld; it will take you about 1.5 hours to learn. Then I would tack weld sheet metal pieces to the back of my firewall covering holes I wanted to fill. Then I would use body filler to finish filling the holes.
