I wouldn't de-bore it. I would short-stoke it, and use longer rods for a better ratio. At 9,000 rpm, with a longer stoke. Your piston speed may be too high for the rings to live.
Here's a quote from a book I read:
Well, the modern Formula 1 engine is an incredible beast with a spec sheet that makes car geeks like me queasy. The basics are out-of-this-world incredible. From just 3.0 liters and 10 cylinders—without horsepower-enhancing turbocharging or supercharging—an F1 engine makes about 900 horsepower. It does this by revving to an incredible 19,000 rpm, or more than double what a rev-happy Honda S2000 engine spins to.
To keep the pistons and connecting rods from flying apart at those revolutions, an F1 piston travels only about 1.6 inches compared with the four-inch stroke of the Corvette Z06 V-8. The bore is roughly 3.80 inches, comparable to the 4.13-inch bore of the Vette's 7.0-liter mill.
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