I think Jim said for every 1 compression point there's about a 3% power gain......more or less so you're spot on and I agree. I believe head flow is the way to go. It's long been my advice not to risk too high a compression on a street car, but no one ever listens. There are a few exceptions where I would push the limit, as in a quench build or an old school over cammed engine, but that's about it. I can give the 400 in Gladys as an example. It's right at 9:1, maybe a tic less but I am extremely happy with the power and torque output. She's got an 8100 pound GVWR and that old girl will get with it when you crack the loud pedal. The Cleveland style heads flow really well.