This just isn't true. The ability of aluminum to reject heat at a quicker rate is way over played. You can't possibly think that aluminum will reject heat fast enough to eleimate detonation because of compression ratio is a bald faced fantasy. You can run the same CR on iron as you can aluminum.
The cooling system is what controls heat rejection.
Got to kill this wrong headed thinking. Been hearing this my whole life and it was wrong then and it's wrong now.