How much quench can I run?

From what I have read 0.040" is about ideal. When I built my 360 I used magnum heads and KB107 flat tops at zero deck with a 0.039" Felpro head gasket. This works out to 10.6:1 compression. The quench area is certainly doing it's thing because I can run 89 octane mid-grade gasoline in this engine with no detonation issues. The timing is 35 total, 12 intial and it's all in by 2300-2400 rpm.