Hmmm...interesting, John!
I tend to worry more about total timing than initial...when you're driving (and especially racing) you will be at total timing for most of the time, while you'll be at initial timing only at startup and idle. You need to find where your engine runs best with the total timing...and what your initial is will depend on how your distributor is set up. If the engine runs best with 39 degrees total, but wants to kick back when you start it, then find what initial works...then you can either sacrifice your total timing or do it right and get your distributor curved. Our cars like 12-14 initial, and depending on compression ratio anywhere from 32-40 degrees total. I've found our lower compression (10:1) L72 likes around 39 degrees while our higher compression L72 (12:1) only likes around 33 degrees. The burn rate of fuels is built into them, which is why there are a gajillion types out there...but generally the race fuels have a faster burn rate, as well as a higher ignition temperature, which help alleviate detonation.