Check my work-Chime in please

This is what i came up with.

Effective chamber = 66.28
62.5 minus 2.4 plus 6.18
(Head chamber - pop-up piston + gasket volume)

Swept volume = 572.74cc (using Pi x radius squared x stroke)

Compression ratio = 9.64:1

(572.74 + 66.28 ) / 66.28 = 9.64


Using wallaceracing.com calculator with your stroke and rod length I get a DCR of 8.47:1 at sea level.

I wouldn't be worried! :)
Just be sure to check all your piston/valve tolerances before final assembly.