Sorry but I'll have to strongly disagree on this one; I have noticed a definite difference in .4 or .5 point and a huge difference in .8 point of CR. This is from putting in 3 different pistons in the same engine in 3 successive racing rebuilds, no other changes. A .4 difference is noticeable for sure; this difference was felt at the bottom end of the torque range but not at the top end.
So for a revving drag race engine with a moderate to high stall converter, probably not so much, but it will make a definite difference for a street/cruiser engine. The 3% DIFFERENCE FOR 1 POINT DIFFERENCE IN COMPRESSION NEEDS TO BE PUT IN ITS PROPER PERSPECTIVE; THIS IS FOR THE PEAK HP NUMBER ONLY, AND IS TOTALLY MISLEADING FOR THE LOW END TORQUE EFFECTS.