Dave, I think the Hemi is a special case when it comes to compression vs. power.

Vizard did a great engine project a few years ago where he dyno tested a SBC with old style dome pistons. Then he took the motor apart, machined some material off the tops of the domes and redid the dyno test. I believe he redid this test 3 times and went from something around 13:1 down to 10:1. If I recall, the power actually went up a small amount as the compression decreased.