How did you mount your radiator (bushing version)?

[ModernMuseum]

I had a recent incident with a PRC radiator that developed a bunch of cracks on each side between the tube/header interface. A racing buddy of mine told me that I need to mount it using rubber bushings.

These radiators (69 camaro / firebird version) utilize a flat plate on each side which mates to the core support. I have some black rubber sheet (roughly 3/16" thick) which I could use to make some squares, possibly several layers thick, at each mounting point.

Would this suffice or is there a better way to do this? What are you guys using?