because your engine has some upgraded modifications and fuel technology is better regulated than it was 50 years ago, I think it's safe for you to continue with your drivability and performance testing you mentioned at the slightly advanced timing value you're at..
detonation, while not always audible to a level that grabs your attention, does generally affect other performance aspects that will give you clues that your combustion rate [with regards to timing in this discussion] is not optimal.. your queries on the subject indicates that you're paying careful attention to a lot more than how much rubber you can burn off the light..
here's an article I found on a quick search, better info is out there, but this will give you a basic understanding of the affects of detonation and common causes..
Eliminating Pre-Ignition & Detonation – Pounding Pistons
good luck!