What gas are you going to run? I'd pick the gas that you're going to run first and then pick the compression ratio to match the gas. If C12 is available in your area then that is a good gas to design around. For a race engine where you're willing to buy race gas like C12 then 13 or 13.5 should be a good safe compression ratio that will allow you to run in any weather. If you already own the pistons then 11.8 would be fine. I made more than 700 hp with less compression than that but that was a fairly trick engine.
