I saw the title of this thread and perked up. "Hey!" I thought, "I'm not the only one in the group who knows about sectional density."
...Until Kona started reeling off formulas. Then it sort of changed to, "Erm. I
thought I knew about sectional density, but really I just know that 1) it's generally good and 2) how to get more in a few circumstances."
Sorry, Kona. Can't help you there. Math makes my eyeballs spin and shuts down my brain.