This sucks. Do you think the reeds may have been touching the walls of the intake, I know my reed stop on the Malossi reed cage slightly touches a tiny part of it. I would imagine your reeds being so many wouldn't need to open up that much i've turned over my engine with a drill to watch the reeds and you can see they barely open but that is at lower rpms.
maybe it was only detonating that day because of the head leak i'm sure timing was fine if you've been blasting. Didn't your hear a whistling sound at low rpm's indicating head leak?
Why waste your time doing weird head stuff. you know it works awesome just be more careful. Puchforum does sell a custom correct head w/squish for the gilardoni but it cost something like $150
2004 + hpi's have the auto retarding curve