Loose truss rod in an H47 electric

Hey Frets Friends- I have been working with a early 60's (i think) harmony H47 guitar. thin, hollow maple body, one pickup, 24 inch scale. it has one of those harmony " steel reinforced neck" stickers, so I think there is a non adjustable metal rod in the neck.

When I rap the neck, the rod rattles and almost every note on the guitar makes it buzz and vibrate. Should I do what frank did on his buzz fixer page and drill a hole in the fingerboard and fill with rubber cement? since I don't have to adjust the rod ever, should I fill it with #10 CA glue. I think that would be easier.

the pickup sounds awesome, BTW and the refret and new tuners and pots have really got this one going. And yes, I have checked every other possible buzz, I really think its the rod.