I can't imagine the geometry of a couple millimeters really having much of an effect...
When you increase rod length, you're decreasing cylinder volume (even though stroke, thus "displacement" is the same). So while you can play more with the gas and air you can get in, does it really still end up more effective than before with more combustible volume, but perhaps harder tuning?
I'm curious, don't know the answer so if anyone is well-qualified, please clarify for me.
