Thanks for sharing first hand experience.
My stroker is a trimmed 12 weight crank and light weight pistons. 2.0 crankpins and destroked to 4.062 to fit in a 250 block.
I don't think my crank stiffness changed much from stock but crank and piston mass are certainly less. I would expect the net effect to be to raise the natural frequency. Combined with your observations gives me some confidence. No data to back this up other than my engine is still together and my flywheel bolts are tight.
