So is it safe to assume that it is not in the 2,500 RPM to 3,500 RPM range? That is where most detonation happens. Your cam should be able to bleed enough pressure to eliminate problems in this area.
On high compression engines, above 5,000 RPMs the pressure can build up again and cause detonation. That can't be fixed with more duration.
Try and pinpoint where the detonation is occuring. Have a friend with a trained ear ride with you.